Subject: wavefunction stability issues

From: Patrick Bultinck <[email-masked]>
Date: Wed, 29 May 2002 18:29:02 +0200

Dear all,

Can anybody refer me to a good reference on the different sources of wave
function instability ? Especially as on how to judge whether a certain post
SCF calculation will help. Also, it is sometimes stated that wave function
instability would indicate the necessity of electron correlation. At this
day and age, only single reference (Hartree-Fock) dynamical electron
correlation techniques can be used for the larger molecules I am looking
at. What good is MP2, CC etc. when the reference is not appropriate ?
Really, for a good result a technique like mrci would be very interesting,
but for some systems (and computer resources), even a large CAS+PT is
impossible. So how to handle this ? Any references ?

As a side question: would anybody have any idea what percentage of post-scf
calculations being done has ever had the stability of its HF reference
checked ?

Thanks,

Patrick Bultinck
Ghent University
Belgium