[molpro-user] non-consecutive frozen-core orbitals

[Adriana Olleta]

Hello, 

I would like to get some help related to how to specify the orbitals that 
should be frozen, if they are not in ascending order of energy. 

If I am running a CCSD calculation for the diatomic NaBr molecule with 
cc-pVDZ basis set for the Na atom and CRENBL ECP + corresponding basis for 
the Br atom, by using G03 and MOLPRO the following problem occurs: 

When running these calculations with G03, five orbitals are frozen which 
correspond to the (1s2s2p) set of the Na atom. In the case of MOLPRO, the 
frozen orbitals additionally include the five 3d orbitals of bromine, 
totalling to a number of ten core orbitals. 

Although the approach of Molpro seems more consistent, I would like to be 
able to reproduce the G03 calculation by performing the same type of 
calculation (with the five core orbitals 1s2s2p(Na)) using Molpro, and at 
the same time correlate the 3d orbitals of Br. 

Since these 3d orbitals lie energetically in between the 1s(Na) and the 
2s(Na) orbitals, it is not possible to freeze 1s2s2p(Na) only by 
specifying "core,5" (i.e., "core,3,1,1,0" in C2v symm). 



Rather, 1s(Na) and four of the five 3d orbitals of Br are frozen, while 
one 3d orbital and 2s2p(Na) are correlated. 

Is there a possibility to freeze orbitals, which are not in consecutive 
energetic ordering? 

Thank you 

Adriana

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