Subject: Beyond Born-Oppenheimer

From: Andrew Horsfield <[email-masked]>
Date: Fri, 7 May 1999 10:12:28 +0100 (GMT)

Dear CCLers,

I am interested in studying non-radiative transitions in silicon, and have
submitted a couple of postings to this list about non-adiabatic molecular
dynamics. In the light of the responses I have received I am now fully
persuaded of the need to have a very accurate description of the
Born-Oppenheimer states in order to determine the small non-adiabatic
correction.

The most transparent way to proceed (I believe) would be to calculate the
full wavefunction as a linear combination of Born-Oppenheimer states for
the ground state and low lying excited states. A harmonic approximation
for the ionic part of the wavefunction would be quite adequate.
Non-radiative transitions could then be found by taking suitable matrix
elements. Can it be done? Would this produce accurate wavefunctions? Are
there standard procedures for doing this?

Best regards,

Andrew

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