[molpro-user] Molpro vs Qchem MP2 single point energy calculation of ethylene differences

[Grant Hill]

Dear Alan,

I’ve no experience with the Qchem program, but I’m guessing that it does not use the frozen core approximation by default. If I change your MP2 directive to {mp2;core,0} I get:

!MP2 total energy                    -78.429489771679

Best regards,

Grant



On 21 Jan 2014, at 20:35, Alan Chien <alandc at umich.edu> wrote:

> Hello all. I'm a new user of Molpro and was running a few little tests on my newly installed 2012.1.9 version of Molpro :D. However, I'm getting some weird results.
> 
> So, I'm comparing an MP2 single point energy calculation of ethylene between Molpro and Qchem.
> 
> I get the same HF energy, but differing MP2 energies at the same geometry.
> 
> Molpro: HF= -78.06321916, MP2= -78.39895488
> Qchem: HF= -78.0632189754, MP2= -78.4294907701
> 
> I looked over my inputs (provided below) and they seem fine…any suggestions? 
> 
> I'll provide outputs if people want them. 
> 
> 
> QCHEM IMPUT
> -----------------------------------------------------------
> $molecule
> 0 1 
> C       -2.0293377388      1.5831581629      0.0000000000 
> C       -0.6979276316      1.6261615210     -0.0000000000
> H       -2.5974389181      2.2373976708      0.6547741027
> H       -2.5540361699      0.8936222030     -0.6547741027
> H       -0.1732292005      2.3156974809      0.6547741027
> H       -0.1298264523      0.9719220131     -0.6547741027
> $end
> 
> $rem
> Exchange HF
> Correlation MP2 
> 
> basis cc-pvtz
> 
> symmetry false
> sym_ignore true
> unrestricted false
> 
> jobtype sp
> $end
> -----------------------------------------------------------
> 
> 
> 
> MOLPRO INPUT
> -----------------------------------------------------------
> ***, Ethylene Geom Opt 
> symmetry=nosym
> geometry={
> C       -2.0293377388      1.5831581629      0.0000000000 
> C       -0.6979276316      1.6261615210     -0.0000000000
> H       -2.5974389181      2.2373976708      0.6547741027
> H       -2.5540361699      0.8936222030     -0.6547741027
> H       -0.1732292005      2.3156974809      0.6547741027
> H       -0.1298264523      0.9719220131     -0.6547741027
> }
> basis=VTZ
> hf
> mp2
> -----------------------------------------------------------
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