[molpro-user] MP2 pair energies

[Grant Hill]

Dear Matthias,

This is because SCS is scaling the opposite (and same) spin contributions, not triplet (and singlet).

If you divide the printed triplet pair energy by a factor of 1.5 you should get the quantity you are looking for.

Hope this helps,
Grant




> On 5 Dec 2017, at 21:02, Matthias Heger <heger at ualberta.ca> wrote:
> 
> I am a bit confused about the MP2 pair energies reported in my calculations. Specifically, my attached example yields:
> 
>> SCS-MP2 correlation energy:           -0.198842375046   (PS=  1.200000  PT=  0.333333)
>> (...)
>> MP2 singlet pair energy              -0.126127623239
>> MP2 triplet pair energy              -0.076321972220
> 
> Scaling the pair energies manually and adding them yields a different energy (-0.176792... Hartree) than given above.
> 
> In addition, I tricked the SCS calculation to only pick up the singlet or triplet pairs with SCSFACS and SCSFACT. That yields SCS correlation energies different from the corresponding pair energies in the output.
> 
> Am I interpreting this wrong?
> 
> Best,
> Matthias
> 
> -- 
> Dr. Matthias Heger
> Department of Chemistry, University of Alberta
> 11227 Saskatchewan Drive NW
> Edmonton, AB T6G 2G2, Canada
> 
> Office: CCIS 4-151
> Lab: CCIS 4-108
> Email: heger at ualberta.ca
> <SCS.out>_______________________________________________
> Molpro-user mailing list
> Molpro-user at molpro.net
> http://www.molpro.net/mailman/listinfo/molpro-user