Discrepancy in MP2 Energy: Molpro vs CFOUR with Dummy Atom

[Nastasia Mauger]

Hello,

I am using Molpro to add dummy atoms at the center of my water cluster, assigning them a 4s4p basis set. I am using the aug-cc-pVDZ basis set for the H and O atoms. THe corresponding Molpro input is attached to this thread.

This setup preserves Ci symmetry and produces the following energies:

MP2/USERDEF energy = -610.060259430164

             MP2              RHF-SCF
   -610.06025943       -608.25885067

However, I find the results a bit surprising. The energy is essentially the same as using aug-cc-pVDZ alone, suggesting that Molpro may have ignored the extra basis set on the dummy atom at the center.

In comparison, CFOUR returns:
HF  = -608.258888668006
MP2 = -610.080541440588

Note the significant difference in MP2 energy , which raises concerns about whether Molpro is correctly incorporating the additional basis functions at the cluster center.

I have attached the corresponding output file.

Thank you!

[peterso...@gmail.com]

Dear Nastasia,

 

The default in Molpro is to not correlate the core electrons while in Cfour the default is to correlate everything.

 

Regards,

 

-Kirk

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