{SPAM}? {SPAM}? Re: [molpro-user] Dipole moment from mp2/rmp2 for (restricted) open shell system

Gerald Knizia knizia at theochem.uni-stuttgart.de
Wed Mar 5 11:24:15 GMT 2008

On Wednesday 05 March 2008 03:14, ishii at tcl.t.u-tokyo.ac.jp wrote:
> You can use 'rs2' command (CASPT2) instead of rmp2.
> In rs2 calculations, dipole moments are calculated.
> Using ROHF as reference in rs2, rs2 is equivalent as RMP2.

This is actually not the entire truth. RS2 and RMP2 both give MP2 results when 
applied to closed shell systems. But in open-shell systems, they differ due 
to using H_0 Hamiltonians for the perturbation theory. For ROHF wave 
functions, RMP2 tends to give better results compared with UCCSD(T) 

That being said, i'm not aware of any way to calculate RMP2 dipole moments 
with the current version of molpro, except using finite fields and finite 
differences (i.e., getting dE/d(dmx)...dE/d(dmz) by adding small finite 
fields to the core Hamiltonian and building difference quotients. See 
"properties and expectation values"/"finite field calculations" in the 
Gerald Knizia

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