# [molpro-user] BSSE with ECP potential/basis

Amit Sharma greifsw at gmail.com
Fri May 6 14:21:26 CEST 2016

```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
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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