[molpro-user] MP2 Calculations - Does Molpro freeze the core electrons for the MP2 method?

[Peterson, Kirk]

Brian,

yes, the default for all correlated calculations in Molpro (including MP2) is to use the frozen-core approximation.  To change from this default, use the "core" directive.

best,

-Kirk

On Jun 11, 2013, at 7:43 AM, Brian Napolion <brian_napolion at yahoo.com<mailto:brian_napolion at yahoo.com>> wrote:

Hello forum,
I have run into a issue with MP2 calculations, and I wonder how this method is implemented in Molpro program.

I need to know if the default in Molpro for MP2 (or other MPn methods) calculations use  the frozen-core approximation, or are all the electrons correlated.

I know the default for restricted-open shell CCSD(T) is frozen core.
I have not  yet run a MP2 calculation (due to the long wait in the que of my computing resources)

If the default is not frozen core, I assume you apply the ACTIVE directive to specify what orbitals are dropped from correlation.

I looked at the Molpro manual and did not get a sure answer.
Thanks in advance to anyone who can help with this.

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