[molpro-user] BSSE with ECP potential/basis

[Amit Sharma]

Hi all,
I want to calculate BSSE where one of the atoms has an ECP potential basis
on it. Should BSSE be computed differently for ECP? There is some
discussion in the literature about switching off the core but I am not sure
how to do that in molpro.

As a test I compute BSSE for two noble gas atoms with AVDZ basis and get a
BSSE of about 47 cm-1. Then I switch the basis on one of the atoms to be
def2-SVPD and I get BSSE which is twice that of the AVDZ result (about 97
cm-1).

However, the CP corrected interaction energy is approximately the same
between the two calculations. 400 cm-1 vs 403 cm-1, so maybe nothing
special needs to be done. Can anyone please help clarify this for me.
Thanks
Amit

***, Ar + he bsse


geometry={Ar

He Ar Rx}


Rx=5.0


!basis=avdz,he=avdz

basis=def2-SVPD,he=avdz



 text,calculation for complex

 hf                            !RHF for total system

 ccsd(t)

 e_Arhe=energy                 !save energy in variable e_Arhe


 text,cp calculation for HE

 dummy,Ar                      !make Ar a dummy

 hf                           !RHF for He

 ccsd(t)

 e_he=energy                   !save energy in variable e_he


 text,cp calculation for Ar

 dummy,he                      !make he dummy

 hf

 ccsd(t)

 e_Ar=energy                   !save energy in variable e_Ar


 text,separate calculation for he

 symmetry,x,y

 geometry={he}                 !geometry for he alone

 hf                            !RHF for He

 ccsd(t)

 e_he_inf=energy               !save energy in variable e_he_inf


 text,separate calculation for Ar

 symmetry,x,y

 geometry={Ar}                 !geometry for Ar alone

 hf                            !scf for Ar

 ccsd(t)

 e_Ar_inf=energy               !save energy in variable e_Ar_inf


de(i)=(e_Arhe-e_he_inf-e_Ar_inf)*tocm    !compute uncorrected interaction
energy

de_cp(i)=(e_Arhe-e_he-e_Ar)*tocm         !compute counter-poise corrected
interaction energy

bsse_he(i)=(e_he-e_he_inf)*tocm          !BSSE for he

bsse_Ar(i)=(e_Ar-e_Ar_inf)*tocm          !BSSE for Ar

bsse_tot(i)=bsse_he(i)+bsse_Ar(i)              !total BSSE
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