Optimization of trial wave functions for use in quantum Monte Carlo with application to LiH

Methods for both partial and full optimization of wavefunction parameters are explored, and these are applied to the LiH molecule. A partial optimization can be easily performed with little difficulty. But to perform a full optimization we must avoid a wrong minimum, and deal with linear-dependency, time step-dependency and ensemble-dependency problems. Five basis sets are examined. The optimized wavefunction with a 3-function set gives a variational energy of -7.998 + 0.005 a.u., which is comparable to that (-7.990 + 0.003) 1 of Reynold's unoptimized \fin ( a double-~ set of eight functions). The optimized wavefunction with a double~ plus 3dz2 set gives ari energy of -8.052 + 0.003 a.u., which is comparable with the fixed-node energy (-8.059 + 0.004)1 of the \fin. The optimized double-~ function itself gives an energy of -8.049 + 0.002 a.u. Each number above was obtained on a Bourrghs 7900 mainframe computer with 14 -15 hrs CPU time.

Name thesis:degree_name

M.Sc. Chemistry

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Faculty of Mathematics and Science

Department dc:contributor.department

Department of Chemistry

Grantor

Brock University

Year dc:date.issued

1988

Author dc:creator

• ChÊ»en, Hung-tÊ»ao.

• Lithium hydride.
• Mathematical optimization.
• Wave functions.
• Monte Carlo method.
• Quantum chemistry.

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/10464/1989

OAI identifier oai:identifier

oai:brocku.scholaris.ca:10464/1989