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Real f-orbital Spherical Harmonic Relationships

Before relationships can be determined, some simple tools must be constructed:

Given that fxyz is normalized, <√(105/16π)xyz/r3√(105/16π)xyz/r3> = 1, then <x2y2z2/r6> = 16π/105.

Given that fz(x2-y2) is normalized,

  <√(105/16π)z(x2-y2)/r3√(105/16π)z(x2-y2)/r3> = 1
then (105/16π)<(z2(x4-2x2y2+y4)/r6)> = 1
but <z2x4/r6> = <z2y4/r6>
therefore (105/16π)<2z2x4/r6> - 2*16π/106 = 1
therefore <z2x4/r6> = 24π/105

 

Given that fz3 is normalized,

  <√(7/16π)z(5z2-3r2)/r3√(7/16π)z(5z2-3r2)/r3> = 1
then (7/16π)<(z2(2z2-3x2-3y2)2/r6)> = 1
therefore (7/16π)<(4z6-12z4x2-12z4y2+18x2y2z2+9x4z2+9y4z2)/r6> = 1
  (7/16π)(<4z6/r6>-6*24π/105+18*16π/105) = 1
or <z6/r6> = 24π/105

To summarize: <x2y2z2/r6> = 16π/105,   <z2x4/r6> = 24π/105,   <z6/r6> = 24π/105

Integrals involving real spherical harmonics are as follows:

f and f harmonics:

The orbitals are normalized, e.g.:

  <fxz2|fxz2> = <(21/32π)x(5z2-r2)/r3(21/32π)x(5z2-r2)/r3>
    = (21/32π)<(x2(4z2-x2-y2)2/r6)>
    = (21/32π)<(x2(16z4+x4+y4-8z2x2-8z2y2+2x2y2)/r6>
    = (21/32π)<(16x2z4 +x6 +x2y4 -8x4z2 -8x2z2y2 +2x4y2)/r6>
    = 21/32π)(11*24π/105+24π/105 -8*16π/105)
    = 1

Most integrals are zero by inspection: if the product involves an odd power, the integral is automatically zero.  The non-zero integrals are:

 

  <fx3|fxz2> = <(7/16π)x(5x2-3r2)/r3√(21/32π)x(5z2-r2)/r3>
    = (7/16π)√(3/2)<(x2(2x2-3y2-3z2)(4z2-x2-y2)/r6)>
    = (7/16π)√(3/2)<(x2(-2x4+3y4-12z4+x2y2+11x2z2-9y2z2)/r6>
    = (7/16π)√(3/2)<(-2x6+3x2y4-12x2z4+x4y2+11x4z2-9x2y2z2)/r6>
    = (7/16π)√(3/2)(-2* 24π/105+3*24π/105-9*16π/105)
    = -√(3/8)
    = <fy3|fyz2>

 

  <fx3|fx(x2-3y2)> = <√(7/16π)<x(5x2-3r2)/r3√(35/32π)x(x2-3y2)/r3>
    =  (7/16π)√(5/2)<(x2(2x2-3y2-3z2)(x2-3y2)/r3>
    = (7/16π)√(5/2)<(x2(2x4+9y4-9x2y2-3x2z2+9y2z2)/r6>
    =  (7/16π)√(5/2)<(2x6+9x2y4-9x4y2-3x4z2+9x2y2z2)/r6>
    = (7/16π)√(5/2)(2*24π/105-3*24π/105+9*16π/105)
    = √(5/8)
    = <fy3|fy(y2-3x2)>

 

  <fx(z2-y2)|fx(x2-3y2)> = <√(105/16π)x(z2-y2)/r3√(35/32π)x(x2-3y2)/r3>
    = (35/16π)√(3/2)<x2(z2x2-3z2y2-x2y2+3y4)/r6>
    = (35/16π)√(3/2)<(x4z2-3x2y2z2-x4y2+3y4x2)/r6>
    = (35/16π)√(3/2)( 24π/105-3* 16π/105- 24π/105+3* 24π/105)
    = √(3/8)
    = <fy(z2-x2)|fy(y2-3x2)>

 

  <fx(z2-y2)|fxz2> = <√(105/16π)x(z2-y2)/r3√(21/32π)x(5z2-r2)/r3>
    = (21/16π)√(5/2)<x2(z2-y2)(4z2-x2-y2)/r6)>
    =  (21/16π)√(5/2)(x2(4z4+y4+x2y2-x2z2-5y2z2)/r6)>
    = (21/16π)√(5/2)(4x2z4+x2y4+x4y2-x4z2-5*x2y2z2)/r6)>
    = (21/16π)√(5/2)(5*24π/105-5*16π/105)
    = √(5/8)
    = <fy(z2-x2)|fyz2>

The complete unitary matrix relating the cubic and axial sets of  f  orbitals is as follows:

          Axial      
    fz3 fxz2 fyz2 fz(x2-y2) fxyz fx(x2-3y2) fy(y2-3x2)
  fx3 0 -√(3/8) 0 0 0 √(5/8) 0
  fy3 0 0 -√(3/8) 0 0 0 √(5/8)
  fz3 1.0 0 0 0 0 0 0
Cubic    fx(z2-y2) 0 √(5/8) 0 0 0 √(3/8) 0
    fy(z2-x2) 0 0 √(5/8) 0 0 0 √(3/8)
    fz(x2-y2) 0 0 0 1.0 0 0 0
  fxyz 0 0 0 0 1.0 0 0

 

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J. J. P. Stewart
Stewart Computational Chemistry, 2007