1. Benchmark Quantum Monte Carlo Calculations for Carbon and Hydrocarbon Species
James B. Anderson, Department of Chemistry, Pennsylvania State University
A combination of a ‘correction scheme’ with ‘correlated sampling’ in Quantum Monte Calculations (QMC) of electronic structure yields accurate values for the wavefunctions and energies of large molecules and the differences in energies for large molecules of similar structures. In the case of the 10-atom carbon ring the accuracies are improved by about a factor of ten over those for independent calculations. Extensions of this hybrid method may be used to optimize trial wavefunctions for such calculations, optimize molecular structures, and determine intermolecular potential energies. The figure illustrates correlated variational, diffusion, and correction calculations in QMC for species A & B.
VQMC
Psi A
Energy A
correlated
correlated
VQMC
Psi B
Energy B
DQMC
Psi A
Energy A
not correlated
DQMC
Psi B
Energy B
VQMC
DQMC
Psi A
Energy A
correlated
correlated
correlated
VQMC
DQMC
Psi B
Energy B