[molpro-user] uccsd(t) energies

[Manhui Wang]

Jose,
    The problem has disappeared with 2009.1. Presumably there was a bug
in 2006.1, but it has been fixed now. See attached tar ball for results
with 2009.1.

Sincerely,
Manhui

Jose A. Gamez wrote:
> Dear all,
> 
> I calculated the energy of the SeCH3 radical at the CCSD(T)/avtz (and 
> MP2/avtz) levels and I obtained the following:
> 
>  **********************************************************************************************************************************
>   
>               UCCSD(T)          RHF-SCF              UMP2            UHF-SCF
>   -2439.71508645  -2439.49831203  -2439.81634192  -2439.50331284
>  **********************************************************************************************************************************
> 
> That the UMP2 energy was lower thant the UCCSD(T) one seemed suspicious, and I 
> was afraid that the ROHF used as reference of the UCCSD(T) was not the lowest 
> state because of the use of the UHF orbitals as initial guess. So I decided to 
> repeat the calculation, just the ROHF and UCCSD(T) parts and I obtained the 
> same ROHF wavefunction in both cases:
> 
> 
>  !RHF STATE 1.1 ENERGY              -2439.498312034134
> 
>  !RHF STATE 1.1 ENERGY              -2439.498312034410
> 
> and therefore the UCCSD(T) had the same reference, although they lead to 
> totally different energies. 
> 
>  !RHF-UCCSD(T) STATE 1.1 ENERGY     -2439.860974666455
> 
>  !RHF-UCCSD(T) STATE 1.1 ENERGY     -2439.715086449912
> 
> The reference energy  and the configuration space for both CCSD(T) calculations 
> were the same, so I don't know the origin of this difference. Does any of you 
> any explanation for this? I attach both output files for more details.
> 
> Thanks for your help
> 
> Cheers,
> 
> Jose
> 
> 
> 
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-- 
-----------
Manhui  Wang
School of Chemistry, Cardiff University,
Main Building, Park Place,
Cardiff CF10 3AT, UK
Telephone: +44 (0)29208 76637
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