AN INTERNAL COORDINATE QUANTUM MONTE-CARLO METHOD FOR CALCULATING VIBRATIONAL GROUND-STATE ENERGIES AND WAVE-FUNCTIONS OF LARGE MOLECULES -A QUANTUM GEOMETRIC STATEMENT FUNCTION-APPROACH
Re. Tuzun et al., AN INTERNAL COORDINATE QUANTUM MONTE-CARLO METHOD FOR CALCULATING VIBRATIONAL GROUND-STATE ENERGIES AND WAVE-FUNCTIONS OF LARGE MOLECULES -A QUANTUM GEOMETRIC STATEMENT FUNCTION-APPROACH, The Journal of chemical physics, 105(13), 1996, pp. 5494-5502
An internal coordinate quantum Monte Carlo (ICQMC) method using import
ance sampling is illustrated for a 100 atom model polyethylene chain.
Importance sampling with an internal coordinate guiding wave function
yields smoother, more physically reasonable wave functions and lower g
round state energies than Cartesian importance sampling, in good agree
ment with normal coordinate analysis results. A novel geometric statem
ent function (GSF) method for economizing expressions involving first
and second derivatives of stretch, bend, and torsion internal coordina
tes by up to 2 orders of magnitude allows QMC calculations to be perfo
rmed even for large molecules in reasonable times on standard workstat
ions. The ICQMC method with quantum GSF is eminently suitable for larg
e molecules with complicated, strongly coupled potential energy surfac
es such as polymer chains.