! Molecular Orbital PACkage (MOPAC)
! Copyright (C) 2021, Virginia Polytechnic Institute and State University
!
! MOPAC is free software: you can redistribute it and/or modify it under
! the terms of the GNU Lesser General Public License as published by
! the Free Software Foundation, either version 3 of the License, or
! (at your option) any later version.
!
! MOPAC is distributed in the hope that it will be useful,
! but WITHOUT ANY WARRANTY; without even the implied warranty of
! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
! GNU Lesser General Public License for more details.
!
! You should have received a copy of the GNU Lesser General Public License
! along with this program.  If not, see <https://www.gnu.org/licenses/>.

subroutine moldat(mode)
!-----------------------------------------------
!
!   If mode == 1 run silently
!   If mode /= 1 generate normal MOPAC output
!
!-----------------------------------------------
!   M o d u l e s
!-----------------------------------------------
!
      use common_arrays_C, only : nfirst, nlast, nat, uspd, txtatm, &
      & pdiag, labels, coord, geo, atmass, na, nbonds, ibonds
!
      USE molmec_C, only : nnhco
!
      USE molkst_C, only : natoms, norbs, nalpha, nbeta, nclose, nopen, &
      & nelecs, fract, numat, mpack, keywrd, n2elec, lm61, moperr, line, &
      & uhf, id, msdel, mol_weight, method_PM6, method_PM7, &
      is_PARAM, formula, ispd, mozyme, nvar, rhf, old_chrge, jobnam, &
      N_3_present, Si_O_H_present, nalpha_open, nbeta_open, pdb_label, &
      method_rm1, use_ref_geo, method_indo, backslash
!
      USE parameters_C, only : natorb, uss, upp, udd, tore, &
      dorbs, zd, zs, zp
!
      USE symmetry_C, only : name
!
      use meci_C, only: nmos
!
      USE chanel_C, only : iw, log, ilog, iarc, archive_fn
!
      use elemts_C, only : elemnt
!
!***********************************************************************
!
!       MOLDAT works out essential molecular data, such as orbital
!              counters (NFIRST, NLAST), number of electrons,
!              starting populations, etc.
!
!***********************************************************************
!-----------------------------------------------
!   I n t e r f a c e   B l o c k s
!-----------------------------------------------
      implicit none
!-----------------------------------------------
!   D u m m y   A r g u m e n t s
!-----------------------------------------------
      integer , intent(in) :: mode
!-----------------------------------------------
!   L o c a l   V a r i a b l e s
!-----------------------------------------------
      integer :: kharge, i, ndorbs, ia, ib, nheavy, nnull, ii, &
        k, k1, j, ielec, ndoubl, ne, nupp, &
        ndown, l, iminr, jminr, icount, &
        ireal, jreal, ni, n1, n4, n9
      integer(8) :: n2elec8
      double precision :: elecs,  c(1), yy, w, sum, rmin   ! c(1) is for a dummy call
      logical :: debug, exci, sing, doub, trip, quar, quin, sext, sept, &
        octe, none, birad, halfe, odd, opend
      character :: num1*1
      double precision, dimension (:), allocatable :: rxyz
      double precision, external :: reada
!-----------------------------------------------
      debug = index(keywrd,'MOLDAT') /= 0
!
!   SPECIAL MODIFIERS FOR LIMITATIONS IN AVAILABLE PARAMETERS
!
      i = index(keywrd,' CHARGE=')
      if (i /= 0) then
        kharge = nint(reada(keywrd,i))
        old_chrge = kharge
      else
        kharge = 0
      end if
      elecs = -kharge
      ndorbs = 0
      if (.not. method_indo .and. uss(1) > (-1.D0)) then
      call mopend (&
           'THE HAMILTONIAN REQUESTED IS NOT AVAILABLE IN THIS PROGRAM')
        return
      end if
!
!  Determine the number of atomic orbitals on each element
!
      if (.not. method_indo) then
        do i = 1,107
          dorbs(i) = (zd(i) > 1.d-8)
          if (dorbs(i)) then
            natorb(i) = 9                   ! Element has "d"-orbitals
          else if (zp(i) > 1.d-20) then
            natorb(i) = 4                   ! Element has "p"-orbitals
          else if (zs(i) > 1.d-20) then
            natorb(i) = 1                   ! Element has one "s"-orbital
          else
            natorb(i) = 0                   ! Element has no orbitals
          end if
        end do
      end if
      numat = 0
      ia = 1
      ib = 0
      nheavy = 0
      nnull = 0
      do ii = 1, natoms
        if (labels(ii)/=99 .and. labels(ii)/=107) then
          numat = numat + 1
          nat(numat) = labels(ii)
          nfirst(numat) = ia
          ni = nat(numat)
          elecs = elecs + tore(ni)
          ib = ia + natorb(ni) - 1
          if (natorb(ni) == 9) ndorbs = ndorbs + 5
          nlast(numat) = ib
          uspd(ia) = uss(ni)
          if (ia /= ib) then
            k = ia + 1
            k1 = ia + 3
            do j = k, k1
              uspd(j) = upp(ni)
            end do
            if (ib > ia) then
              nheavy = nheavy + 1
            else
              nnull = nnull + 1
            end if
            if (k1 /= ib) then
              k = k1 + 1
              uspd(k:ib) = udd(ni)
            end if
          end if
        end if
        ia = ib + 1
      end do
      if (numat == 1) then
        if (index(keywrd,'FORCE') /= 0 .and. index(keywrd,' THERMO') == 0) then
          call mopend ('A SINGLE ATOM HAS NO VIBRATIONAL MODES')
          return
        end if
      end if
      if (mode /= 1) call refer
      call gmetry (geo, coord)
      if (mode /= 1)then
        call empiri()
        write(iw,"(/,a,/)") trim(formula)
        if (moperr) return
      end if
      allocate(rxyz((numat*(numat + 1))/2), stat = i)
      if (i /= 0) then
        if (mode /= 1) call mopend("The interatomic distance array could not be assigned")
!
!  Do not attempt to check interatomic distances, or anything related to the geometry
!
        return
      end if
      if (pdb_label .and. index(keywrd, " GEO-OK") + index(keywrd, " 0SCF") == 0) then
!
!  Sanity check - does the atom name match its label?
!
        l = 0
        if (index(keywrd, "RESIDUES") == 0) then
          do i = 1, numat
            j = labels(i)
            if (j /= 1 .and. (j < 6 .or. j > 8)) cycle
!
!  Check H, C, N, and O, only
!
              if (txtatm(i)(14:14) >= 'a' .and. txtatm(i)(14:14) <= 'z') &
              txtatm(i)(14:14) = char(ichar(txtatm(i)(14:14)) + ichar("A") - ichar("a"))
            if(elemnt(j)(2:2) /= txtatm(i)(14:14) .and. elemnt(j)(2:2) /= txtatm(i)(13:13)) then
              if (j == 1 .and. txtatm(i)(13:13) == "D") then
                txtatm(i)(13:13) = "H"
              else if (j == 1 .and. txtatm(i)(14:14) == "D") then
                txtatm(i)(14:14) = "H"
              else
                num1 = char(Int(log10(i + 0.5)) + ichar("2"))
                write(line,'(a,i'//num1//',a,a)')"Atom name for atom", i, &
                " ("//elemnt(j)(2:2)//") does not match its label """//txtatm(i)//""""
                write(iw,'(10x,a)')trim(line)
                l = l + 1
                if (l == 20) then
                  write(iw,'(/10x,a)') "Remaining errors not printed"
                  exit
                end if
              end if
            end if
          end do
        end if
        if (l > 0) then
          call mopend("Atom name does not match atom label. To suppress this error, add GEO-OK")
          return
        end if
      end if
!
!   WRITE OUT THE INTERATOMIC DISTANCES
!
      l = 0
      iminr = 0
      jminr = 0
      rmin = 100.D0
      do i = 1, numat
        do j = 1, i
          l = l + 1
          rxyz(l) = sqrt((coord(1,i) - coord(1,j))**2 + &
                         (coord(2,i) - coord(2,j))**2 + &
                         (coord(3,i) - coord(3,j))**2)
          if (.not.(rmin > rxyz(l) .and. i /= j .and. (nat(i) < 103 .or. nat(j) < 103))) cycle
          iminr = i
          jminr = j
          rmin = rxyz(l)
        end do
      end do
      call setcup
      if (moperr) return
!
!  The "or" here is needed because symmetry theory uses connectivity
!  (If "or" is replaced by "and" a really weird bug is introduced. DON'T DO IT!
!
      if (index(keywrd, " ADD-H") == 0 .or. index(keywrd, " PDBOUT") /= 0 ) then
        call set_up_dentate
        call check_cvs(index(keywrd, " GEO-OK") .ne. 0)
        if (moperr) return
        call check_H(i)
        if (i /= 0) then
          if (Index (keywrd, " 0SCF") + Index (keywrd, " RESEQ") + Index (keywrd, " SITE=") +  &
            Index (keywrd, " GEO-OK") + Index (keywrd, " ADD-H") + Index (keywrd, " LET") == 0) then
            write(iw,'(10x,a)') "Add keyword ""LET"" to allow job to continue"
            call mopend ("A hydrogen atom is badly positioned")
            if ( index(keywrd," PDBOUT") /= 0) then
              inquire(unit=iarc, opened=opend)
              if (opend) close(iarc)
                line = archive_fn(:len_trim(archive_fn) - 3)//"pdb"
                if (index(keywrd, " HTML") /= 0) then
                  do i = len_trim(line), 1, -1
                    if (line(i:i) == "/" .or. line(i:i) == backslash) exit
                  end do
                end if
              open(unit=iarc, file=trim(line), status='UNKNOWN', position='asis')
              rewind iarc
              call pdbout(iarc)
            end if
          end if
        end if
      end if
      if (use_ref_geo) call big_swap(0,1)
      if (id == 0) then
        if ((index(keywrd, " ADD-H") == 0 .and. .not. mozyme) .or. numat < 200) then
          call symtrz (c, pdiag, 1, .FALSE.)
          if (moperr) return
          if (mode /= 1) write (iw, '(2/''      MOLECULAR POINT GROUP   :   '',A4)') name
        end if
      end if
      mol_weight = 0.D0
      do i = 1, numat
        mol_weight = mol_weight + atmass(i)
      end do
      mpack = 1
      if (Index (keywrd, " RESEQ") + index(keywrd,' 0SCF') + index(keywrd,' ADD-H') &
        + index(keywrd,' SITE')/= 0) return
      n9 = 0
      n4 = 0
      n1 = 0
      do i = 1, natoms
        j = labels(i)
        if (j > 0 .and. j /= 99 .and. j /= 107) then
          k = natorb(j)
          if (k == 1) then
            n1 = n1 + 1
          else if (k == 4) then
            n4 = n4 + 1
          else if (k == 9) then
            n9 = n9 + 1
          end if
        end if
      end do
      ispd = n9
      if (id == 0) then
        n2elec8 = (n4*(n4 - 1))/2
        n2elec8 = 100*n2elec8 + 2025*n9 + 100*n4 + n1 + 2025*(n9*(n9 - 1))/2 + 450*n9*n4 + 45*n9*n1 + &
     &  10*n4*n1 + (n1*(n1 - 1))/2 + 10
      else
        n2elec8 = (n4*(n4 + 1))/2
        n2elec8 = 100*n2elec8 + 2025*n9 + 100*n4 + n1 + 2025*(n9*(n9 + 1))/2 + 450*n9*n4 + 45*n9*n1 + &
     &  10*n4*n1 + (n1*(n1 + 1))/2 + 10
      end if
      if (.not. mozyme .and. n2elec8 > 2147483647) then
        if (Index (keywrd, " RESEQ") + Index (keywrd, " SITE=") + index(keywrd, " ADD-H") == 0) then
          call mopend(" Data set '"//trim(jobnam)//"' exists, but is too large to run.")
          write(iw,'(10x,a)')"(Maximum number of two-electron integrals allowed: 2,147,483,647)"
          write(iw,'(10x,a, i12,a)')"(Number of two-electron integrals exceeded this by:", &
            n2elec8 - 2147483647,")"
          write(iw,'(/10x,a)')"(Try using MOZYME on this system)"
          return
        end if
      end if
      n2elec = int(n2elec8, kind(n2elec))
      if (ispd > 0 .and. index(keywrd, " ESP") /= 0) then
        line = " The ESP method does not work with 'd' orbitals"
        write(iw,'(//,10x,a)')trim(line)
        call mopend(trim(line))
        if (method_pm6) then
          write(iw,'(10x,a)')" (If possible, use MNDO, AM1, or PM3, with a 1SCF to prevent geometry changes)"
        end if
        return
      end if
!
!  Set all solid-state variables at this point
!
      lm61 = 45*n9 + 10*n4 + n1
      norbs = nlast(numat)
      if (index(keywrd, " GRAPH") /= 0) then
        if (norbs > 9500) then
          write(line,'(a)')" The system is too large for 'GRAPH' to be used."
          write(iw,'(//10x,a,/)')trim(line)
          call mopend(trim(line))
          return
        end if
      end if
      if (id /= 0) then
        i = max(18, norbs)
      else
        i = norbs
      end if
      mpack = (i*(i+1))/2
!
!   NOW TO CALCULATE THE NUMBER OF LEVELS OCCUPIED
!
      sing = index(keywrd,' SING') /= 0
      doub = index(keywrd,' DOUB') /= 0
      trip = index(keywrd,' TRIP') /= 0
      quar = index(keywrd,' QUAR') /= 0
      quin = index(keywrd,' QUIN') /= 0
      sext = index(keywrd,' SEXT') /= 0
      sept = index(keywrd,' SEPT') /= 0
      octe = index(keywrd,' OCTE') /= 0
      none = index(keywrd,' NONE') /= 0
      exci = index(keywrd,' EXCI') /= 0
      birad = exci .or. index(keywrd,'BIRAD')/=0
      if (index(keywrd,'C.I.')/=0 .and. uhf) then
        write (iw, '(2/10X,''C.I. NOT ALLOWED WITH UHF '')')
        call mopend ('C.I. NOT ALLOWED WITH UHF')
        return
      end if
!
! NOW TO WORK OUT HOW MANY ELECTRONS ARE IN EACH TYPE OF SHELL
!
      nalpha = 0
      nbeta = 0
!
!      PROTECT DUMB USERS FROM DUMB ERRORS!
!
      nelecs = nint(max(elecs,0.D0))
      nelecs = min(2*norbs,nelecs)
      if (.not. rhf .and. .not. uhf) then
        if (mod(nelecs,2) == 0) then
          rhf = .true.
        else
          uhf = .true.
        end if
      end if
      if (method_indo .and. uhf) then
        write(iw,'(10x,a)')" INDO does not support UHF - defaulting to ROHF"
        rhf = .true.
        uhf = .false.
      end if
      if (uhf) then
        if (index(keywrd," POLAR") /= 0) then
            write(iw,'(//10x,a)')" Keyword POLAR used with an odd-electron system."
            write(iw,'(10x,a)')" By default, UHF is used for odd-electron systems."
            write(iw,'(10x,a)')" POLAR does not work with UHF."
            write(iw,'(10x,a)')" To correct this fault, add RHF to the keyword line, and re-run."
            call mopend("POLAR used with a UHF system.  Add keyword RHF and re-run")
            return
          end if
          if (index(keywrd," ESP") /= 0) then
            write(iw,'(//10x,a)')" Keyword ESP used with a UHF calculation."
            write(iw,'(10x,a)')" By default, UHF is used for odd-electron systems."
            write(iw,'(10x,a)')" ESP does not work with UHF."
            write(iw,'(10x,a)')" To correct this fault, add RHF to the keyword line, and re-run."
            call mopend("ESP used with a UHF system.  Add keyword RHF and re-run")
            return
          end if
      end if
      odd = (mod(nelecs,2) /= 0)
!
! Explicit (named) declaration of spin state
!
      msdel = 100000 ! Set to a very high value, so if it is explicitly set, that will be obvious
      if (sing) then
        if (odd) then
         call mopend (&
             'SINGLET SPECIFIED WITH ODD NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' SINGLET STATE CALCULATION'')')
          msdel = 0
        end if
      else if (doub) then
        if (.not. odd) then
         call mopend (&
             'DOUBLET SPECIFIED WITH EVEN NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' DOUBLET STATE CALCULATION'')')
          msdel = 1
        end if
      else if (trip) then
        if (odd) then
         call mopend (&
             'TRIPLET SPECIFIED WITH ODD NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' TRIPLET STATE CALCULATION'')')
          msdel = 2
        end if
      else if (quar) then
        if (.not. odd) then
          call mopend (&
             'QUARTET SPECIFIED WITH EVEN NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' QUARTET STATE CALCULATION'')')
          msdel = 3
        end if
      else if (quin) then
        if (odd) then
          call mopend (&
             'QUINTET SPECIFIED WITH ODD NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' QUINTET STATE CALCULATION'')')
          msdel = 4
        end if
      else if (sext) then
        if (.not. odd) then
          call mopend (&
             'SEXTET SPECIFIED WITH EVEN NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' SEXTET STATE CALCULATION'')')
          msdel = 5
        end if
      else if (sept) then
        if (odd) then
          call mopend (&
             'SEPTET SPECIFIED WITH ODD NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' SEPTET STATE CALCULATION'')')
          msdel = 6
        end if
      else if (octe) then
        if (.not. odd) then
          call mopend (&
             'OCTET SPECIFIED WITH EVEN NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' OCTET STATE CALCULATION'')')
          msdel = 7
        end if
      else if (NONE) then
        if (odd) then
          call mopend (&
             'NONET SPECIFIED WITH ODD NUMBER OF ELECTRONS, CORRECT FAULT')
          return
        else
          if (mode /= 1) write (iw, '(2/'' NONET STATE CALCULATION'')')
          msdel = 8
        end if
      end if
!
!  Generic declaration of spin state
!
      i = Index (keywrd, " MS")
      if (i /= 0) then
        if (msdel < 100000) then
          write(iw,'(a)')" MS cannot be used with other keywords that define spin"
          write(iw,'(a)')" Specify either MS or other keyword, but not both."
          call mopend("MS cannot be used with other keywords that define spin")
          call to_screen(" MS cannot be used with other keywords that define spin")
          call to_screen(" Specify either MS or other keyword, but not both.")
          return
        end if
        i = Nint (2*reada (keywrd, Index (keywrd, " MS")))
        if((odd .eqv. mod(i,2) == 0)) then
          write(iw,"(/10x,a,i5)")"Number of electrons in system =", nelecs
          write(iw,"(10x,a,f5.1)")"Value of MS supplied          =  ", i*0.5d0
          if (odd) then
            write(iw,'(10x, a)')"Number of electrons is odd, but MS is integer "//&
              "implying number of electrons is even."
          else
            write(iw,'(10x, a)')"Number of electrons is even, but MS is not integer "//&
              "implying number of electrons is odd."
          end if
          write(iw,"(10x,a)")"Correct the error and re-submit"
          call mopend ("Value of MS not consistent with number of electrons")
          return
        end if
        i = index(keywrd,' MS')
        if (i /= 0) then
          msdel = nint(2.d0*reada(keywrd,index(keywrd,' MS')))
          if (Mod(nelecs+msdel,2) == 1) then
            write (iw, '(//10 x, "Impossible value of MS ")')
            call mopend ("Impossible value of MS")
            return
          end if
        end if
      end if
      if (msdel > 99999) msdel = 0 ! Set default value of msdel

!
! At this point, msdel is known. Now work out UHF and RHF quantities
!
      if (uhf) then
        nbeta = (nelecs - msdel)/2
        nalpha = nelecs - nbeta
        nopen = 0
        nclose = 0
        fract = 0.d0
        nalpha_open = nalpha
        nbeta_open = nbeta
        if (mode /= 1 .and. .not. mozyme) write (iw, &
    '(2/10X,''UHF CALCULATION, NO. OF ALPHA ELECTRONS ='',I5,/27X, &
    & ''NO. OF BETA  ELECTRONS ='',I5)') nalpha, nbeta
        i = index(keywrd,'OPEN(')
        if (i /= 0) then
          j = index(keywrd(i:i+10),',') + i - 1
          nmos = nint(reada(keywrd,j))
          ielec = nint(reada(keywrd,index(keywrd,'OPEN(') + 5))
          fract = (ielec*1.d0)/nmos
          if (nclose < 0) then
            call mopend ('IMPOSSIBLE NUMBER OF FILLED SHELLS')
            return
          end if
        else
          ielec = 0
          nmos = 0
        end if
          nalpha = nalpha - ielec
          if (nalpha < 0) then
            call mopend ('NUMBER OF ALPHA ELECTRONS IS LESS THAN ZERO')
            return
          end if
         nalpha_open = nalpha + nmos
         nbeta_open = nbeta
      else  !  The RHF option
!
!   NOW TO DETERMINE OPEN AND CLOSED SHELLS
!
        ielec = 0
        nmos = 0
        fract = 0
        if (exci .or. birad) then
          if (mode /= 1) then
            if (birad) write (iw, '(2/'' SYSTEM IS A BIRADICAL'')')
            if (exci) write (iw, '(2/'' EXCITED STATE CALCULATION'')')
          end if
          if (odd) then
            write (iw, &
      '(2/10X,''SYSTEM SPECIFIED WITH ODD NUMBER OF ELECTRONS, CORRECT FAULT '')')
            call mopend (&
               'SYSTEM SPECIFIED WITH ODD NUMBER OF ELECTRONS, CORRECT FAULT')
            return
          end if
          ielec = 2
          nmos = 2
        else if ((nelecs/2)*2 /= nelecs) then
          ielec = 1
          nmos = 1
        end if

        i = index(keywrd,'OPEN(')
        if (i /= 0) then
          j = index(keywrd(i:i+10),',') + i - 1
          nmos = nint(reada(keywrd,j))
          ielec = nint(reada(keywrd,index(keywrd,'OPEN(') + 5))
        end if
        nclose = nelecs/2
        nopen = nelecs - nclose*2
        if (ielec /= 0 .and. norbs > 0) then
          if (((nelecs/2)*2 == nelecs .neqv. (ielec/2)*2 == ielec)) then
            write (iw, '(/10x, A,I5)') ' NUMBER OF ELECTRONS IN SYSTEM:    ', nelecs
            write (iw, '(10x, A,I5)') ' NUMBER OF ELECTRONS IN OPEN SHELL:', ielec
            call mopend ('IMPOSSIBLE NUMBER OF OPEN SHELL ELECTRONS')
            return
          end if
          nclose = nclose - ielec/2
          nopen = nmos
          if (nclose + nopen > norbs) then
            write (iw, '(/10x, A,I5)') 'TOTAL NUMBER OF ELECTRONS:                      ', nelecs
            write (iw, '(10x, A,I5)') 'NUMBER OF ELECTRONS IN PARTIALLY-FILLED LEVELS: ', ielec
            write (iw, '(10x, A,I5)') 'NUMBER OF DOUBLY FILLED LEVELS:                 ', nclose
            write (iw, '(10x, A,I5)') 'NUMBER OF PARTLY FILLED LEVELS:                 ', nopen
            write (iw, '(10x, A,I3)') 'NUMBER OF DOUBLY FILLED PLUS PARTLY FILLED LEVELS:', &
              nclose + nopen
            write (iw, '(10x, A,I5)') 'TOTAL NUMBER OF ORBITALS:                       ', nopen
            call mopend (&
       'NUMBER OF DOUBLY FILLED PLUS PARTLY FILLED LEVELS IS GREATER THAN THE TOTAL NUMBER OF ORBITALS')
            return
          end if
          if (nmos == 0) then
            write (iw, *) ' NUMBER OF M.O.s IN OPEN(M,N) IS ZERO!'
            call mopend (' NUMBER OF ELECTRONS IN OPEN(M,N) IS ZERO!')
            return
          end if
          fract = ielec*1.D0/nmos
          if (nclose < 0) then
            write (iw, '(A)') ' IMPOSSIBLE NUMBER OF CLOSED SHELLS'
            call mopend ('IMPOSSIBLE NUMBER OF CLOSED SHELLS')
            return
          end if
          if (mode /= 1) write (iw, '(/6X,''THERE ARE'',I5,'' DOUBLY FILLED LEVELS'')') nclose
        end if
        if (mode /= 1 .and. .not. mozyme) then
          num1 = char(Int(log10(nclose + 0.5)) + ichar("2"))
          write (iw, '(2/6X,''RHF CALCULATION, NO. OF DOUBLY OCCUPIED LEVELS ='',I'//num1//',/)') nclose
          if (nopen/=0 .and. abs(fract-1.D0)<1.D-4) &
            write (iw, '(/23X,''NO. OF SINGLY OCCUPIED LEVELS ='',I5)') nopen
          if (nopen/=0 .and. abs(fract-1.D0)>1.D-4) &
            write (iw, '(/23X,''NO. OF LEVELS WITH OCCUPANCY'',F6.3,''  ='',I3)') fract, nopen
        end if
        i = index(keywrd,'C.I.=(')
        if (i /= 0) then
          j = index(keywrd(i:i+10),',') + i - 1
          ndoubl = nint(reada(keywrd,j))
          if (ndoubl > nclose) then
            write (iw, '(7x,A,I3)') 'NUMBER OF DOUBLY FILLED LEVELS IN C.I. RESET TO', nclose
            ndoubl = nclose
          end if
          i = nint(reada(keywrd,index(keywrd,'C.I.=(') + 5))
          i = i - ndoubl
          if (nopen > i) then
            call mopend ('NUMBER OF OPEN-SHELLS ALLOWED IN C.I. IS LESS THAN THAT SPECIFIED BY OTHER KEYWORDS')
            return
          end if
          if (i + nclose > norbs) then
            write(iw,'(10x,a,i2)')"Number of doubly-occupied levels requested in C.I.:", ndoubl
            write(iw,'(10x,a,i13)')"Total number of M.O.s requested in C.I.:", i + ndoubl
            write(iw,'(10x,a,i2)')"Calculated number of empty M.O.s requested in C.I.:", i
            write(iw,'(10x,a,i13)')"Index of highest M.O. requested in C.I.:", nclose + i
            write(iw,'(10x,a,i13)')"Number of M.O.s in system:              ", norbs
            call mopend ('NUMBER OF M.O.s REQUESTED IN C.I. IS GREATER THAN THE NUMBER OF ORBITALS')
            return
          end if
        end if
        nopen = nopen + nclose
      end if
      if (index(keywrd, " CIS") /= 0) then
        msdel = 0
        else
!
!  WORK OUT IF DEFINED SPIN-STATE ALLOWED
!

      end if
      if (msdel/=0 .and. .not. uhf) then
!
!   MSDEL = NUMBER OF ALPHA ELECTRONS - NUMBER OF BETA ELECTRONS
!
        ndoubl = 99
        i = index(keywrd,'C.I.=(')
        if (i /= 0) then
          j = index(keywrd(i:i+10),',') + i - 1
          ndoubl = nint(reada(keywrd,j))
          nmos = nint(reada(keywrd,index(keywrd,'C.I.=(') + 5))
        else if (index(keywrd,'C.I.=') /= 0) then
          nmos = nint(reada(keywrd,index(keywrd,'C.I.=') + 5))
        else
          nmos = nopen - nclose
          nmos = min0(norbs,nmos)
        end if
        if (ndoubl == 99) then
          j = max(min((nclose + nopen + 1)/2 - (nmos - 1)/2, norbs - nmos + 1),1)
        else
          j = nclose - ndoubl + 1
        end if
        ne = int(max(0.D0,nclose - j + 1.D0)*2.D0 + &
          max(0.D0,(nopen - nclose)*fract) + 0.5D0)
        nupp = (ne + msdel)/2
        ndown = ne - nupp
        if (nmos == 0) then
          nupp = 0
          ndown = 0
        end if
        if (.not. method_indo) then
!
!  NUPP  = NUMBER OF ALPHA ELECTRONS IN ACTIVE SPACE
!  NDOWN = NUMBER OF BETA  ELECTRONS IN ACTIVE SPACE
!
          if (nupp*ndown < 0 .or. nupp > nmos .or. ndown > nmos .or. nmos == 0) then
            write (iw, '(A)')' SPECIFIED SPIN COMPONENT NOT SPANNED BY ACTIVE SPACE'
            write (iw, '(a,i3)')' Number of alpha electrons in active space:', nupp
            write (iw, '(a,i3)')'  Number of beta electrons in active space:', ndown
            write (iw, '(a,i3)')'                      Size of active space:', nmos
            if (Index (keywrd, " MS") /= 0) then
              call web_message(iw,"ms.html")
            else
              call web_message(iw,"active_space.html")
            end if
            call mopend ('SPECIFIED SPIN COMPONENT NOT SPANNED BY ACTIVE SPACE')
            return
          end if
        end if
      end if
      halfe = (nopen > nclose .and. Abs(fract -2.D0) > 1.d-20 .and. Abs(fract) > 1.d-20 &
      & .or. index(keywrd,'C.I.')/=0)
      if (halfe) halfe = (.not. (index(keywrd,'EXCI') /= 0 .or. &
                                 index(keywrd,'ROOT') /= 0 .and. index(keywrd,'ROOT=1') == 0))
      if (halfe .and. id /= 0 .and. index(keywrd,' NOANCI') == 0) then
        write (iw, *)
        write (iw, *) ' ''NOANCI'' MUST BE USED FOR RHF OPEN-SHELL SYSTEMS'
        write (iw, *) ' THAT INVOLVE TRANSLATION VECTORS'
        call mopend (&
       '"NOANCI" MUST BE USED FOR RHF OPEN-SHELL SYSTEMS THAT INVOLVE TRANSLATION VECTORS')
        return
      end if
      yy = dble(kharge)/(norbs + 1.D-10)
      pdiag(:norbs) = 0.D0
      do i = 1, numat
        ni = nat(i)
        if (nlast(i) - nfirst(i) == (-1)) cycle
        l = nfirst(i) - 1
        if (nlast(i) - nfirst(i) == 0) then
!
!    Hydrogen
!
          l = l + 1
          pdiag(l) = tore(ni) - yy
        else if (nlast(i) - nfirst(i) == 3) then
!
!    Normal heavy atom
!
          w = tore(ni)*0.25D0 - yy
          pdiag(l+1:4+l) = w
        else
!
!   This atom has a 'd' shell
!
          if (ni<21 .or. ni>30 .and. ni<39 .or. ni>48 .and. ni<57) then
!
!   Main Group Element:  The "d" shell is formally empty.
!
            w = tore(ni)*0.25D0 - yy
            pdiag(l+1:4+l) = w
            l = 4 + l
            pdiag(l+1:5+l) = -yy
          else if (ni < 99) then
!
!   Transition metal
!
            sum = tore(ni) - 9*yy
!   First, put 2 electrons in the 's' shell
            l = l + 1
            pdiag(l) = max(0.D0,min(sum,2.D0))
            sum = sum - 2.D0
            if (sum > 0.D0) then
!
!   Now put as many electrons as possible into the 'd' shell
!
              l = l + 3
              do j = 1, 5
                l = l + 1
                pdiag(l) = max(0.D0,min(sum*0.2D0,2.D0))
              end do
              sum = sum - 10.D0
              if (sum > 0) then
!
!   Put the remaining electrons in the 'p' shell
!
                l = l - 8
                pdiag(l+1:3+l) = sum/3.D0
              end if
            end if
          end if
        end if
      end do
      call setup_nhco(ii)
!
!  Does the system contain a N bonded to three atoms, at least
!  two of which are not hydrogen atoms?
!
      do i = 1, numat
        if (nat(i) == 7 .and. nbonds(i) == 3) then
        j = 0
        if (nat(ibonds(1,i)) == 1) j = 1
        if (nat(ibonds(2,i)) == 1) j = j + 1
        if (nat(ibonds(3,i)) == 1) j = j + 1
        if ( j < 2)  N_3_present = .true.
        end if
        if (N_3_present) exit
      end do
!
!  Does the system contain a Si-O-H group?
!
      do i = 1, numat
        if (nat(i) == 14) then
          do j = 1, nbonds(i)
            if (nat(ibonds(j,i)) == 8) then
              l = ibonds(j,i)
              do k = 1, nbonds(l)
                if (nat(ibonds(k,l)) == 1) Si_O_H_present = .true.
              end do
            end if
          end do
        end if
        if (Si_O_H_present) exit
      end do
  !    Si_O_H_present = .false.
      if (nvar == 0) then
        if (index(keywrd," GRAD") /= 0) then
          if (index(keywrd, " RESEQ") + index(keywrd, " ADD-H") + index(keywrd, " SITE") == 0) then
            line = " Keyword GRADIENTS used, but geometry has no variables."
            call mopend(trim(line))
            return
          end if
        end if
      end if
      if (mod(nelecs, 2) == 1 .and. .not. uhf .and. nnhco > 0 .and. mode /= 1 &
      .and. (index(keywrd," 1SCF") == 0 .or. index(keywrd," GRAD") /= 0) .and. &
      nvar > 10 .and. index(keywrd," GEO-OK") == 0 .and. abs(kharge) < 400) then
      write(iw,"(/)")
       write(iw,"(10x,a)") &
       " This system has an odd number of electrons and also", &
       " contains peptide linkages.  The CPU time required for", &
       " calculating the gradients is likely to be large. If ""UHF"" is ", &
       " added, then the gradient calculation will run much faster. ", &
       " Either add ""GEO-OK"" or ""UHF"" to the keyword list.", &
       " Also, check that the system should be a radical. A quick " , &
       " way to do this is to add keyword ""LEWIS"" and run it again.", &
       " This will print out the Lewis structure."
       call mopend("radical run with RHF.  Either add 'GEO-OK' or 'UHF'.")
       return
      end if
      if (nnhco > 3 .and. &
        index(keywrd," GEO-OK") == 0 .and. &
        index(keywrd," RESEQ") == 0 .and. &
        index(keywrd," CHARGES") == 0 .and. &
        index(keywrd," 1SCF") == 0) then
        j = 1
        do i = 1, natoms
          if (na(i) > 0) j = j + 1
        end do
        if (nvar > 0 .and. j == natoms .and. .not. is_PARAM) then
          if (index(keywrd," ADD-H") + index(keywrd," SITE=") == 0) then
            write(iw,"(5x,a)")"The system contains peptide linkages, but all atoms are in internal coordinates.", &
            "This is likely to result in problems in geometry optimization.", &
            "To correct this, add ""XYZ"" to the keyword line.", &
            "(If internal coordinates should be used, add ""GEO-OK"" to the keyword line.)"
            call mopend("Peptides should be run using Cartesian coordinates")
            return
          end if
        end if
      end if
      if (mode /= 1 .and. ii > 1) then
        write (iw, '(A,I4,2A)') ' THERE ARE', ii/2, ' PEPTIDE LINKAGES IDENTIFIED IN THIS SYSTEM'
        write (iw, '(A)') ' Keyword "NOMM" has been used, therefore a Molecular Mechanics correction will not be used'
      else if (mode /= 1 .and. nnhco /= 0 .and. (method_RM1 .or. method_pm6 .or. method_PM7) &
      & .and. (index(keywrd, "MMOK") == 0)) then
        if (index(keywrd, " LEWIS") + index(keywrd, " RESEQ") + index(keywrd, " CHARGES")== 0) then
          if (method_RM1) line = "RM1"
          if (method_PM6) line = "PM6"
          if (method_PM7) line = "PM7"
      !      write (iw, '(A)') ' When peptide bonds are present, and '//line(:3)//&
      !      &' is used, then keyword "MMOK" or "NOMM" must be used'
      !      call mopend("Keyword MMOK or NOMM must be used with "//line(:3)//" for this system")
      !      return
          end if
      end if
      if (mode /= 1 .and. index(keywrd,'PRTINT') /= 0) then
        write (iw, '(2/10X,''  INTERATOMIC DISTANCES'')')
        call vecprt (rxyz, numat)
      end if
      if (rmin < 0.9D0 .and. index(keywrd,'CHECK') /= 0 .or. &
          rmin < 0.2D0 .and. index(keywrd,'GEO-OK') == 0 .or. &
          rmin < 1.d-4) then
        icount = 0
        ireal = iminr
        jreal = jminr
        do i = 1, natoms
          if (labels(i)==99 .or. labels(i)==107) cycle
          icount = icount + 1
          if (icount == iminr) ireal = i
          if (icount /= jminr) cycle
          jreal = i
        end do
        write(line,"('ATOMS',i6,' AND',i6,' ARE SEPARATED BY',f7.4,' ANGSTROMS.')")ireal, jreal, rmin
        if (index(keywrd,'CHECK') /= 0) then
          call mopend(trim(line))
          write(iw,'(/10x,a)')'FAULT DETECTED BY KEYWORD "CHECK'
          if (log) write (ilog, '(//10x,a,//10x,a)')trim(line), 'FAULT DETECTED BY KEYWORD "CHECK'
        else
          call mopend(trim(line))
          write(iw,'(/10x,a)')'TO CONTINUE CALCULATION SPECIFY "GEO-OK"'
          num1 = char(Int(log10(max(ireal,jreal)     + 1.0)) + ichar("1"))
          if (pdb_label) then
            write(iw,"(/10x,a,i"//num1//",a)")"(Label for atom ", ireal, ": """//txtatm(ireal)//""")"
            write(iw,"( 10x,a,i"//num1//",a)")"(Label for atom ", jreal, ": """//txtatm(jreal)//""")"
          end if
          if (log) write (ilog, '(//10x,a,//10x,a)')trim(line), 'TO CONTINUE CALCULATION SPECIFY "GEO-OK"'
        end if
        write (iw, '(/,a)')'   NOTE THAT THE ATOM NUMBERS CORRESPOND TO THE'//&
          ' ''CARTESIAN COORDINATES'' ATOM LIST.'
        if (index(keywrd,' ADD-H') /= 0) then
          write(line,'(a,i6,a,i6)')'SEVERE ERROR IN GEOMETRY, FIX FAULT BEFORE CONTINUING. Atoms:',ireal, ' and', jreal
          call mopend (trim(line))
          numat = 0
          natoms = 0
          return
        end if
        if (rmin < 1.d-4) then
          write(line,'(a,i6,a,i6)')'GEOMETRY IN ERROR, FIX FAULT BEFORE CONTINUING. Atoms:',ireal, ' and', jreal
          call mopend (trim(line))
        else
          call mopend ("GEOMETRY IN ERROR.  TO CONTINUE CALCULATION SPECIFY 'GEO-OK'.")
        end if
        return
      end if
      if (.not.debug) return
      write (iw, 290) numat, norbs, ndorbs, natoms
  290 format('   NUMBER OF REAL ATOMS:',i4,/,'   NUMBER OF ORBITALS:  ',i4,/,&
        '   NUMBER OF D ORBITALS:',i4,/,'   TOTAL NO. OF ATOMS:  ',i4)
      write (iw, 300) (uspd(i),i=1,norbs)
  300 format('   ONE-ELECTRON DIAGONAL TERMS',/,10(/,10f8.3))
      write (iw, 310) (pdiag(i),i=1,norbs)
  310 format('   INITIAL P FOR ALL ATOMIC ORBITALS',/,10(/,10f8.3))
      return
end subroutine moldat

subroutine setcup
   !***********************************************************************
   !
   !   SETCUP determines CUTOFP and the number of unit cells in each
   !          direction that will be needed in order to allow CUTOFP
   !   to be correctly used.
   !
   !***********************************************************************
    use molkst_C, only: cutofp, id, keywrd, l1u, l2u, l3u, l123, l11, l21, l31, line, &
      clower
    use common_arrays_C, only : tvec
    use chanel_C, only: iw
    implicit none
    integer :: i
    double precision :: area12, area13, area23, r1, r12, r13, r2, &
         & r23, r3, tv1, tv2, tv3, vol, sum
    double precision, external :: reada, volume
    cutofp = 1.d10
    l1u = 0
    l2u = 0
    l3u = 0
    l123 = 1
    if (id == 0) return
    i = Index (keywrd, " CUTOFP")
    if (i /= 0) then
      cutofp = reada (keywrd, i+7)
    else
      cutofp = 30.d0
    end if
!
!   Set constants for truncation function.
!
!   CLOWER = lower bound of truncation function, as a function of CUTOFP
!
! Setting "clower" to 17 Angstroms seems to be okay for the gradients and for smoothness of the PES.
! It had been 14 Angstroms, but that caused significant problems with the gradients.
!
!  If in doubt, test the gradients using DERITR
!
    clower = Min( cutofp*2.d0/3.d0, 17.0d0)
   !
   !   CALCULATE L1U, L2U, and L3U
   !
    if (id == 1) then  !   Polymer case
      !
      !   TV1 =  length of polymer.
      !
      tv1 = Sqrt (tvec(1, 1)**2+tvec(2, 1)**2+tvec(3, 1)**2)
      if (tv1 < 1.d0) then
        line = "  Length of translation vector is too small."
        write(iw,'(a)')trim(line)
        call mopend (trim(line))
        return
      end if
      l1u = Int (cutofp*4.d0/3.d0/tv1) + 1
    else if (id == 2) then !  Layer system
      !
      !   TV1, TV2 = Distances across unit cell.
      !
      r1 = Sqrt (tvec(1, 1)**2 + tvec(2, 1)**2 + tvec(3, 1)**2)
      r2 = Sqrt (tvec(1, 2)**2 + tvec(2, 2)**2 + tvec(3, 2)**2)
      if (r1 < 1.d0) then
        call mopend ("Length of first translation vector is too small.")
        return
      end if
      if (r1 < 1.d0) then
        call mopend ("Length of second translation vector is too small.")
        return
      end if
      r12 = Sqrt ((tvec(1, 2)-tvec(1, 1))**2 + (tvec(2, 2)-tvec(2, 1))**2 &
           & + (tvec(3, 2)-tvec(3, 1))**2)
      sum = (r1**2 + r2**2 - r12**2)/(2*r1*r2)
      if (sum > 0.9d0) then
        call mopend ("The angle between the two translation vectors is too small")
        return
      end if
      tv1 = r1 * Sin (Acos((r1**2 + r2**2 - r12**2)/(2*r1*r2)))
      tv2 = r2 * Sin (Acos((r1**2 + r2**2 - r12**2)/(2*r1*r2)))
      l1u = Int (cutofp*4.d0/3.d0/tv1) + 1
      l2u = Int (cutofp*4.d0/3.d0/tv2) + 1
    else !  Solid-state (three-dimensional crystal)
      !
      !   TV1,TV2,TV3 = Distances between faces of unit cell
      !
      r1 = Sqrt (tvec(1, 1)**2 + tvec(2, 1)**2 + tvec(3, 1)**2)
      r2 = Sqrt (tvec(1, 2)**2 + tvec(2, 2)**2 + tvec(3, 2)**2)
      r3 = Sqrt (tvec(1, 3)**2 + tvec(2, 3)**2 + tvec(3, 3)**2)
      if (r1 < 1.d0 .or. r2 < 1.d0 .or. r3 < 1.d0) then
        if (r1 < 1.d0) then
          line = "  Length of first translation vector is too small."
          write(iw,'(a)')trim(line)
          call mopend (trim(line))
          return
        else if (r2 < 1.d0) then
          line = "  Length of second translation vector is too small."
          write(iw,'(a)')trim(line)
          call mopend (trim(line))
          return
        else
          line = "  Length of third translation vector is too small."
          write(iw,'(a)')trim(line)
          call mopend (trim(line))
          return
        end if
      end if
      r12 = Sqrt ((tvec(1, 2)-tvec(1, 1))**2 + (tvec(2, 2)-tvec(2, 1))**2 &
           & + (tvec(3, 2)-tvec(3, 1))**2)
      r13 = Sqrt ((tvec(1, 3)-tvec(1, 1))**2 + (tvec(2, 3)-tvec(2, 1))**2 &
           & + (tvec(3, 3)-tvec(3, 1))**2)
      r23 = Sqrt ((tvec(1, 3)-tvec(1, 2))**2 + (tvec(2, 3)-tvec(2, 2))**2 &
           & + (tvec(3, 3)-tvec(3, 2))**2)
      area12 = r1 * r2 * Sin (Acos((r1**2 + r2**2 - r12**2)/(2*r1*r2)))
      area13 = r1 * r3 * Sin (Acos((r1**2 + r3**2 - r13**2)/(2*r1*r3)))
      area23 = r2 * r3 * Sin (Acos((r2**2 + r3**2 - r23**2)/(2*r2*r3)))
      vol = volume (tvec, id)
      if (vol < 1.d0) then
        write (iw,'(//10X,A,F9.6,A)') &
             & "Volume of unit cell unreasonably small:", vol, &
             & " Cubic Angstroms"
        call mopend("Volume of unit cell unreasonably small")
        return
      end if
      tv1 = vol / area23
      tv2 = vol / area13
      tv3 = vol / area12
      sum = 4.0d0
      if ((tv1 < sum .or. tv2 < sum .or. tv3 < sum) .and. Index (keywrd, " GEO-OK") == 0) then
        write(iw,"(//10x,a,f9.3,a   )") "Translation vector length 1:", r1," Angstroms"
        write(iw,"(  10x,a,f9.3,a   )") "Translation vector length 2:", r2," Angstroms"
        write(iw,"(  10x,a,f9.3,a,/ )") "Translation vector length 3:", r3," Angstroms"
        if (tv1 < sum) write (iw,'(10X,A,F6.3,A,f6.3)') &
             & "Distance between faces 2 and 3 is unreasonably small:", tv1," Angstroms, min:", sum
        if (tv2 < sum) write (iw,'(10X,A,F6.3,A,f6.3)') &
             & "Distance between faces 1 and 3 is unreasonably small:", tv2," Angstroms, min:", sum
        if (tv3 < sum) write (iw,'(10X,A,F6.3,A,f6.3)') &
             & "Distance between faces 1 and 2 is unreasonably small:", tv3," Angstroms, min:", sum
        if (tv1 < sum .or. tv2 < sum .or. tv3 < sum) then
          call mopend("One or more translation vectors are unreasonably small")
        write(iw,'(10x,a)')"To over-ride this safety check, add keyword 'GEO-OK'"
        return
        end if
      end if
      l1u = Int ((cutofp*4.d0/3.d0)/tv1) + 1
      l2u = Int ((cutofp*4.d0/3.d0)/tv2) + 1
      l3u = Int ((cutofp*4.d0/3.d0)/tv3) + 1
    end if
    l123 = (2*l1u + 1)*(2*l2u + 1)*(2*l3u + 1)
    l11 = min(l1u,1)
    l21 = min(l2u,1)
    l31 = min(l3u,1)
end subroutine setcup
subroutine write_cell(iprt)
  use molkst_C, only: mol_weight, escf, numat, keywrd, gnorm, &
   line, mers, density, gui
  use funcon_C, only: fpc_10
  use common_arrays_C, only: nat, tvec
  use ef_C, only : nstep
  implicit none
  integer, intent(in) :: iprt
  integer :: i, j, k, l, z, m, old_nstep = -1
  double precision :: ta, tb, tc, tab, tbc, tac, talpha, tbeta, tgamma, vol
  integer, dimension (100) :: nel
  double precision, external :: reada, volume
  save :: old_nstep
  if (iprt < 0 .or. gui) return
  if (iprt == 0) then
    if(old_nstep == nstep) return
    old_nstep = nstep
  end if

!
!  Write out unit cell lengths and angles
!
  ta = Sqrt(tvec(1,1)**2 + tvec(2,1)**2 + tvec(3,1)**2)
  tb = Sqrt(tvec(1,2)**2 + tvec(2,2)**2 + tvec(3,2)**2)
  tc = Sqrt(tvec(1,3)**2 + tvec(2,3)**2 + tvec(3,3)**2)
  tab = Sqrt((tvec(1,1)-tvec(1,2))**2 + (tvec(2,1)-tvec(2,2))**2 + (tvec(3,1)-tvec(3,2))**2)
  tac = Sqrt((tvec(1,1)-tvec(1,3))**2 + (tvec(2,1)-tvec(2,3))**2 + (tvec(3,1)-tvec(3,3))**2)
  tbc = Sqrt((tvec(1,3)-tvec(1,2))**2 + (tvec(2,3)-tvec(2,2))**2 + (tvec(3,3)-tvec(3,2))**2)
  talpha = 57.295779513d0*Acos((tb**2 + tc**2 - tbc**2)/(2*tc*tb))
  tbeta  = 57.295779513d0*Acos((ta**2 + tc**2 - tac**2)/(2*ta*tc))
  tgamma = 57.295779513d0*Acos((ta**2 + tb**2 - tab**2)/(2*ta*tb))
  tab = 1.d0
  if (index(keywrd," BCC") /= 0) tab = 2.d0
!
!  Work out the empirical formula
!
  i = Index(keywrd, " Z=")
  if (i /= 0) then
    i = Nint(reada(keywrd,i))
    z = mers(1)*mers(2)*mers(3)*i
    if (Index (keywrd, " BCC") /= 0) z = z/2
  else
    nel = 0
    do i = 1, numat
      nel(nat(i)) = nel(nat(i)) + 1
    end do
    j = 0
    do i = 1, 100
      if (nel(i) > 0) then
        j = j + 1
        nel(j) = nel(i)
       end if
    end do
    k = 10000
    do i = 1, j
      if(nel(i) < k) k = nel(i)
    end do
!
!  k is the smallest number of atoms of any element in the formula
!
    do i = 1, 20
      m = 0
      do l = 1, j
        if (Abs((i*nel(l))/k - (i*1.d0*nel(l))/k) > 1.d-5) m = 1
      end do
      if (m == 0) exit
    end do
!
!  Number of empirical units  = k/i
!
    z = k/i
  end if
  vol = volume (tvec, 3)
  if (mers(1) > 0 .and. mers(2) > 0 .and. mers(3) > 0 .and. index(keywrd, " PRT ") == 0) then
    if (gnorm > 1.d-20) then
      write (line,'(i4,a,3f7.3,3f7.2,a,f8.2,a,f6.3,a,f10.3, a, f7.2)')nstep + 1," a, b, c, alpha, beta, gamma:", &
      & tab*ta/mers(1), tab*tb/mers(2), tab*tc/mers(3), talpha, tbeta, tgamma, &
      " Vol:",vol/(mers(1)*mers(2)*mers(3))," Density:",mol_weight * 1.d24 / fpc_10 / vol, &
      " HoF:",escf/z," Grad:",gnorm/sqrt(z*1.d0)
      write(iprt,"(a)")line(:len_trim(line))
    end if
  end if
  if (index(keywrd, " PRT ") /= 0) then
    write (iprt, '(/10X,A,F15.3,A)') 'VOLUME OF UNIT CELL     =', &
        vol/(max(1,mers(1))*max(1,mers(2))*max(1,mers(3))), ' CUBIC ANGSTROMS'
    write (iprt, '(/10X,A,F15.3,A)') 'DENSITY                 =', density, ' GRAMS/CC'

    write (iprt,'(28x, a, 8x, f7.3, a)')"  A   =", tab*ta/max(1,mers(1)), " ANGSTROMS"
    write (iprt,'(28x, a, 8x, f7.3, a)')"  B   =", tab*tb/max(1,mers(2)), " ANGSTROMS"
    write (iprt,'(28x, a, 8x, f7.3, a)')"  C   =", tab*tc/max(1,mers(3)), " ANGSTROMS"
    write (iprt,'(28x, a, 8x, f7.3, a)')"ALPHA =",talpha, " DEGREES"
    write (iprt,'(28x, a, 8x, f7.3, a)')"BETA  =",tbeta , " DEGREES"
    write (iprt,'(28x, a, 8x, f7.3, a)')"GAMMA =",tgamma, " DEGREES"
    call l_control("PRT", 3, -1)
  end if
  return
end subroutine write_cell
subroutine write_unit_cell_HOF(iprt)
  use molkst_C, only : keywrd, escf, numat, line, mers, formula
  use common_arrays_C, only : nat
  implicit none
  integer, intent(in) :: iprt
  integer :: i, j, k, l, z, nel(107), m
  character :: num*1
  logical :: one_letter
  double precision, external :: reada

    if (iprt < 0) return
!
!  Work out the empirical formula
!
        i = Index(keywrd, " Z=")
        if (i /= 0) then
          i = Nint(reada(keywrd,i))
          z = max(1, mers(1))*max(1, mers(2))*max(1, mers(3))*i
          if (Index (keywrd, " BCC") /= 0) z = z/2
        else
          nel = 0
          do i = 1, numat
            nel(nat(i)) = nel(nat(i)) + 1
          end do
          j = 0
          do i = 1, 100
            if (nel(i) > 0) then
              j = j + 1
              nel(j) = nel(i)
            end if
          end do
          k = 1000
          do i = 1, j
            if(nel(i) < k) k = nel(i)
          end do
!
!  k is the smallest number of atoms of any element in the formula
!
          do i = 1, 10
            m = 0
            do l = 1, j
              if (Abs((i*nel(l))/k - (i*1.d0*nel(l))/k) > 1.d-5) m = 1
            end do
            if (m == 0) exit
          end do
!
!  Number of empirical units  = k/i
!
         z = k/i
       end if
       num = char(ichar("2") + int(log10(z + 0.05)))
       write (line, "(10x,'H.o.F. per unit cell    =',f17.5,' KCAL, for',i"//num//",' unit cells')") &
         & escf/z, z
       i = index(formula, ":") + 1
       write(line(len_trim(line) + 1:), '(a)')", unit cell ="
       one_letter = .true.
       do
         if (formula(i:i) == "=") exit
         if (formula(i:i) == " ") then
           i = i + 1
           cycle
         end if
         if (formula(i:i) < "0" .or. formula(i:i) > "9") then
           j = j + 1
           if (one_letter) then
             line(len_trim(line) + 2:) = formula(i:i)
           else
             line(len_trim(line) + 1:) = formula(i:i)
           end if
           i = i + 1
           one_letter = .false.
         else
           l = index(formula(i:), " ") + i
           k = nint(reada(formula, i))/z
           num = char(ichar("1") + int(log10(k + 0.05)))
           write(line(len_trim(line) + 1:),'(i'//num//')') k
           i = l
           one_letter = .true.
         end if
       end do
       if (iprt == 0) then
         call to_screen(line)
       else
         write(iprt,"(a)")line(:len_trim(line))
       end if
       return
      end subroutine write_unit_cell_HOF
      subroutine write_pressure(iprt)
      use common_arrays_C, only: loc, tvec, na
      use molkst_C, only: nvar, pressure, line, press
      use funcon_C, only: fpc_10
      use common_arrays_C, only : grad, xparam, labels
      implicit none
      integer, intent(in) :: iprt
      integer :: m, i1,i2, k, l, i, ndim
      double precision :: xi
      double precision, dimension (nvar) :: dsum, dsum1
      double precision, external :: ddot, volume
      if (iprt < 0) return
        m = 0
        i1 = 0
        i2 = 0
        ndim = 0
        do i = 1, nvar
          k = loc(1, i)
          l = labels(k)
          xi = xparam(i)
          if (l == 107 .and. (m == 0 .or. k == i1)) then
!
!  Atom is a Tv
!
            i1 = k
            m = m + 1
            dsum(m) = grad(i)
            dsum1(m) = xparam(i)
            if (m == 3) then
              if (na(k) /= 0) then
                if (iprt == 0) then
                  call to_screen("The pressure required to constrain translation vectors")
                  call to_screen("can only be calculated if Cartesian coordinates are used.")
                else
                  if (Abs(pressure) > 0.01d0) then
                    write(iprt,'(/10x,a)')"The pressure required to constrain translation vectors"
                    write(iprt,'(10x,a)')"can only be calculated if Cartesian coordinates are used."
                  end if
                end if
                return
              end if
!
!  Determine the scalar of the component of the gradient vector in the
!  direction of the translation vector
!
              xi = ddot(3,dsum, 1,dsum1,1)
!
!  Convert this into a pressure = force per unit area
!
              xi = -(4184.d0*10.d0**30)/fpc_10 * xi/volume (tvec, 3)
              if (Abs(xi) < 1.d-20) cycle ! suppress printing if gradients are zero
              if (i2 == 0) then
                write(line,'(a)') "          Pressure required to constrain translation vectors"
                if (iprt == 0) then
                  call to_screen(trim(line))
                else
                  write(iprt,*)trim(line)
                end if
                i2 = 1
              end if
              xi = (xi - pressure * (4184.d0*10.d0**30)/ fpc_10)*1.d-9
              ndim = ndim + 1
              press(ndim) = xi
              write(line,'(10x,a,i4,a,f7.2,a)')"Tv(", k,")  Pressure:",xi," GPa"
               if (iprt == 0) then
                  call to_screen(trim(line))
                else
                  write(iprt,*)trim(line)
                end if
              m = 0
            end if
          end if
        end do
  end subroutine write_pressure
  subroutine setup_nhco(ii)
  USE molmec_C, only : nnhco, nhco, htype
  USE molkst_C, only : numat,  method_am1, method_pm3, method_mndo, method_pm6, method_PM7, method_rm1, &
   keywrd
  use common_arrays_C, only : nat
  implicit none
  integer, intent (out) :: ii
!
!  Local
!
  integer :: j, i, k, l, m, jj
  double precision, external :: distance

  nnhco = 0
  !
  !   SET UP MOLECULAR-MECHANICS CORRECTION TO -(C=O)-(NH)- LINKAGE
  !   THIS WILL BE USED IF NOMM HAS NOT BEEN SPECIFIED.
  !
                      htype = 0.d0
    if (method_mndo) htype = 6.1737D0
    if (method_am1)  htype = 3.3191D0
    if (method_pm3)  htype = 7.1853D0
    if (method_rm1)  htype = 2.4127D0
    if (method_pm7)  htype = 3.1595D0
    if (method_pm6)  htype = 2.5000D0
    ii = 0
    if (index(keywrd,'NOMM') /= 0) ii = 1
  !
  !   IDENTIFY O=C-N-H SYSTEMS VIA THE INTERATOMIC DISTANCES MATRIX
  !
  l230: do j = 1, numat
      if (nat(j) /= 6) cycle  l230
      do i = 1, numat
        if (nat(i) /= 8) cycle
        if (distance(i, j) > 1.3D0) cycle
        do k = 1, numat
          if (nat(k) /= 7) cycle
          if (distance(k, j) > 1.6D0) cycle
          do l = 1, numat
            if (nat(l) /= 1) cycle
            if (distance(k, l) > 1.3D0) cycle
  !
  !   WE HAVE A H-N-C=O SYSTEM.  THE ATOM NUMBERS ARE L-K-J-I
  !   NOW SEARCH OUT ATOM ATTACHED TO NITROGEN, THIS SPECIFIES
  !   THE SYSTEM X-N-C=O
  !
            l190: do m = 1, numat
              if (m==k .or. m==l .or. m==j) cycle  l190
              if (distance(m, k) > 1.7D0) cycle  l190
              do jj = 1, nnhco, 2
                if (nhco(3,jj) /= k) cycle
                cycle  l190
              end do
              nnhco = nnhco + 1
              nhco(1,nnhco) = i
              nhco(2,nnhco) = j
              nhco(3,nnhco) = k
              nhco(4,nnhco) = m
              nnhco = nnhco + 1
              nhco(1,nnhco) = i
              nhco(2,nnhco) = j
              nhco(3,nnhco) = k
              nhco(4,nnhco) = l
              if (ii /= 0) then
                ii = ii + 2
                nnhco = nnhco - 2
              end if
              cycle  l230
            end do l190
          end do
        end do
      end do
  end do l230
    end subroutine setup_nhco
