[molpro-user] Computation of the dipole moment with CCSD(T)
Lorenzo Lodi
l.lodi at ucl.ac.uk
Mon Sep 11 20:07:25 BST 2006
Thanks everyone for the exaustive replies. I see that things are not
completely straighforward and it'll take me a while to read some of the
suggested literature.
By the way, I must specify that my goal is to calculate the dipole to an
accuracy of 1.e-4 so that even "small" differences matter to me.
I am also doing calculations with the MRCI (and ACPF, AQCC) methods and
I have some doubts here as well...
How are the dipole values reported as "!MRCI STATE 1.1 DIPOLE MOMENTS"
calculated? Are they equivalent to the expectation value of the dipole
on the MRCI wavefunction?
I calculated the dipole with the finite-field approach (near equilibrium
geometry, aug-cc-pCVDZ basis set, 6-orbitals CAS) and I found for the
MRCI dipole a difference with the value reported by molpro of about
5.e-3 a.u.
(I thorougly adjusted the various threshold parameters and the field
strength so the difference is not a numerical artefact)
Is there any theoretical reason why either of these values should be
considered "sounder" than the other?
Would it make sense to take the difference between the two values as
some estimate of the error in the dipole?
Thanks again
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