[molpro-user] ump2 method in molpro is different from the one in gaussian?

[Kirk Peterson]

Dear Lydia,

it looks to me that different numbers of electrons are probably being correlated in the two
jobs.  In the case of ECP-based calculations, the default frozen core in Gaussian is often
very different from that of Molpro.

regards,

Kirk

On Mar 18, 2011, at 2:54 PM, lydia wrote:

> Hi all,
> I found the ump2 calculation in molpro get different energy from the
> one of Gaussian, but they have the same UHF energies.
> 
> This is from molpro:
> The input file is
> {uhf;orbprint,10;maxit,200;
> wf,85,1,1;closed,16,10,11,5;occ,17,10,11,5;}
> {ump2;
> orbital,IGNORE_ERROR;
> closed,16,10,11,5;
> occ,17,10,11,5;
> wf,85,1,1;}
> and output file is
> 1PROGRAM * UMP2 (Unrestricted open-shell)
> Reference energy                   -1463.161083731141
> Correlation energy                    -2.548208935082
> !UMP2 STATE 1.4 Energy             -1465.709292666223
> 
> This is from gaussian:
> HF=-1463.1610804
> MP2=-1467.12587
> 
> Since they have the same UHF energy, the wavefunction, orbitals etc
> are the same. The difference can only come from the correlation energy
> calculation.
> So I want to know the methodolody for UMP2 is different in Molpro and
> gaussian? I checked the molpro manule and did not get any useful
> information for that. If you have some experiences, please share with
> me. Thanks in advance.
> 
> lydia
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