VPT effective geometry?

[Lukáš Félix Pašteka]

Dear all,

Is there an option to print out effective (vibrationally averaged) geometries in the VPT2 calculation?

The module conveniently prints effective rotational constants, but not effective geometries by default. In case these are also calculated internally, could they be printed? 

Otherwise, this can be calculated by hand using the printed cubic force constants and harmonic displacement vectors, but doing this manually is a little cumbersome and error-prone.

Best

Lukas

[rauhut]

Dear Lukas,

vibrationally averaged geometries are currently not implemented in the VPT2 program, but as you have the quartic force field readily available, you can use the VSCF and VCI programs to print them. Your input should look like this

{xsurf

 vtaylor,type=qff

 disk,extern='your external restart file'}

vibstate,ubound=0

poly,type=qff

vscf,pot=poly

vci,pot=poly

This will compute just the vibrational ground state and will then print vibrationally averaged atomic position (R_a) and vibrationally averaged bond lengths (R_g). Usually, using a quartic force field within VSCF and VCI calculations is not the very best idea, but as you are only interest in the vibrational ground state this is a sufficiently good approximation and should provide fairly good results.

Best regards,

     Guntram