[molpro-user] What is spin ordering in doubly occupied CI vector entries?
Dr. Seth Olsen
s.olsen1 at uq.edu.au
Thu Oct 11 00:24:44 BST 2007
Hi Molpro-Users,
I have questions about what conventions Molpro may follow when printing
out the CI vector from an MCSCF calculation.
1. What is the spin ordering in a doubly occupied orbital? For example
if a determinant is listed as '2ab', then are the spins in the doubly
occupied orbital ordered in the same way as the singly occupied ones -
'ab' in the above case? Is there a convention for spin-ordering in
determinants like '220', where there are not singly occupied states to
judge by? It seems this could make a big difference in wavefunction
analyses, because swapping the spin ordering of a pair of electrons will
change the sign. Is there a way to get Molpro to print out a more
detailed notation for the determinants?
2. I have noticed that almost all of the time, 2 determinants with the
same number occupations ( '2ab' and '2ba', for example) will print out
with the 'beta-first' configuration preceeding the 'alpha-first' (that
is, if '2ab' and '2ba' form a CSF with equal and opposite coefficients,
then '2ba' will print first, followed by '2ab' with the sign of the
coefficient reversed). Is there any significance to rare cases where
the order is reversed (i.e. where '2ab' prints before '2ba')? Is this
just due to numerical inaccuracies which cause the determinants to have
very small differences in magnitude and which lead the program to print
the 'higher' magnitude contribution first?
I would really appreciate it if someone would enlighten me on this
topic. I've been pouring over a set of CI vectors for weeks to try and
extract a VB-type analysis of the wavefunction for a multi-state
calculation. There are conical interesections involved, and I want to
be able to figure out what the right sign is for various contributions
to the wavefunction for each state, and to be able to untangle orbital
phase changes from CI vector phase changes. Thank you very much for
your time.
Many Thanks,
Seth
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Dr Seth Olsen, PhD
Postdoctoral Fellow, Biomolecular Modeling Group
Centre for Computational Molecular Science
Australian Institute For Bioengineering and Nanotechnology (75)
The University of Queensland
Brisbane Qld 4072 Australia
Tel: +61 7 3346 3946
Fax: +61 7 3346 3992
email: s.olsen1 at uq.edu.au
Web: www.ccms.uq.edu.au
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