Faults specific to PM7

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The following faults in PM7 were discovered after publication of the method.  Users are advised to be aware of these faults when using PM7.  Please report faults in PM7 that are not on this list to openmopac@gmail.com


Fault No.  

Date reported






February 28, 2013



  Charge on Al is unreasonable: -2.45
C-Al distance is ~0.5Å too long
  Calculations where a hydrogen atom is near to an aluminum atom should be avoided. Use PM6 instead.
2   December 29, 2013   Watson-Crick
Guanine-Cytosine base pair
  Optimized geometry is not planar   This error is small but definite. The planar form is 0.83 kcal/mol higher than the non-planar form.  Probably it will not affect results for proteins or DNA-type systems significantly.  The error is caused by the hydrogen bond approximation used in PM7.
3   March 11, 2014   Donor-acceptor complex
  A P-F covalent bond is predicted   The P-F interaction is not repulsive enough at VDW distances.  This might be due to the core-core terms.  An attempt will be made to correct this fault.
4   June 23 2014   DNA-type systems are best modeled using PM6-DH+.  PM7 gives N-H - N hydrogen bonds that are too long.
5   May 22 2015   Phenylalanine   Cα-Cβ-Cγ angle is 110.0°, should be 113.6°   Registers as an error with MolProbity. Fault common to aromatic residues.
6   May 22 2015   Proteins   Non-bonding residues are too close together   Registers as an error with MolProbity.
7   November 30 2015   Cl-Cu-P(Ph)3   Cu - P distance too large   Results for systems with Cu bonded to P will be very inaccurate - use PM6 instead.
8 April 20 2016 hexachlorobenzene crystal and in crystalline Cl2 Cl - Cl non-bonded distances are too small The heat of sublimation is incorrect.
9   May 20 2016       Silver - silver interactions are inaccurate.    
10   June 22 2017   (CH3)3Si-O-Si(CH3)3   Si-O-Si angle is 180°   Geometries of Si-O-Si molecules will be faulty.  Most minerals are not affected because of other strong interactions.