Format of Inputs

Parmhess requires the following files as input:

  1. LOG file of a QM frequency calculation by Gaussian.
  2. FCHK file of a QM frequency calculation by Gaussian.
  3. MM input file in Gaussian format. Includes charges, atom types and MM functions.
  4. A file named “input.inp” that includes the filename of all above.

The LOG and FCHK file should be generated from a QM frequency calculation with “freq=intmodes”. The FCHK file should be generated by formchk -3 foo.chk foo.fchk. The “-3” flag is important otherwise the internal Hessian will not be written into FCHK files.

An example of MM input file in Gaussian format is as follows.

mmH2O2.com:

%mem=1gb
#p amber=softonly geom=connectivity nosymm
iop(4/33=3,7/33=1)
freq=intmodes

MM

0 1
O-oh--0.410452   -0.718633164030   -0.118472295063   -0.054617618503
H-ho-0.410452   -1.023538245240    0.665457463989    0.436707052760
O-oh--0.410452    0.718637032315    0.118468958072   -0.054573365001
H-ho-0.410452    1.023507272500   -0.665430766999    0.436820814218

 1 2 1.0 3 1.0
 2
 3 4 1.0
 4

AmbTrs ho oh oh ho 0 0 0 0 0.0 XXXXXX 0.0 0.0 1.0
HrmBnd1 ho oh oh XXXXXX 100.2486
HrmStr1 ho oh XXXXXX 0.97412
HrmStr1 oh oh XXXXXX 1.45667
Nonbon 3 1 0 0 0.0 0.0 0.5 0.0 0.0 -1.2
VDW ho  0.0000  0.0000
VDW oh  1.7210  0.2104

The unknown parameters to be determined should be written as “XXXXXX”.

Preparing input files manually could be complicated. Tsubasa program was designed to automate these processes.