[molpro-user] 回复: Re: 回复: Re: UCCSD-F12 with CASSCF orbitals
knizia at theochem.uni-stuttgart.de
Thu Aug 11 20:21:38 BST 2011
> Dear Kirk,
> Thanks again for your suggestion. I am not sure what is the intrinsic
> reason for the incorrect anwsers in such case, but in my case it seems
> to be good. I did some test for hoco system and the results obtained
> from hf/uccsd(t)-f12 and hf/multi/hf/uccsd(t)-f12 are almost the same.
> Here I mean the energies for H+CO2, trans-hoco and cis-hoco minimum
> relative to OH+CO, the total energies for each geometry are of course
> different in such two cases. Note that the results are also close to
> experimental measurements. So are these results meaningless or
> coincidence? Please let me know if I was wrong.
The problem with the uccsd(t)-f12 program was that it would effectively
count the RHF orbital relaxation within the MO basis twice when used
with non-HF orbitals (once as part of the normal CCSD(T) singles energy
and once as part of EF12_RHFRELAX). You should be able to get a good
approximation to the correct energy by using (ENERGY - EMP2_SINGLES
instead of just ENERGY as a work-around (EF12_RHFRELAX would be the CABS
relaxation energy and EMP2_SINGLES the RMP2 singles energy within the MO
basis) . This has been fixed in the development version, but as far as I
know not in the production version.
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