@article {6439, title = {Inclusion of trial functions in the Langevin equation path integral ground state method: Application to parahydrogen clusters and their isotopologues}, journal = {Journal of Chemical Physics}, volume = {140}, year = {2014}, pages = {234101}, abstract = {

We developed and studied the implementation of trial\ wavefunctions\ in the newly proposed\ Langevin equation\ Path Integral\ Ground State\ (LePIGS) method [S. Constable, M. Schmidt, C. Ing, T. Zeng, and P.-N. Roy,\ J. Phys. Chem. A\ 117, 7461 (2013)]. The LePIGS method is based on the Path Integral\ Ground State(PIGS) formalism combined with Path Integral Molecular Dynamics sampling using a\ Langevin equation\ based sampling of the canonical distribution. This LePIGS method originally incorporated a trivial trial\ wavefunction,\ ψT, equal to unity. The present paper assesses the effectiveness of three different trial\ wavefunctions\ on three\ isotopes\ of hydrogen for\ cluster\ sizes\ N\ = 4, 8, and 13. The trial\ wavefunctions\ of interest are the unity trial\ wavefunction\ used in the original LePIGS work, a Jastrow trial\ wavefunction\ that includes correlations due to hard-core repulsions, and a\ normal mode\ trial\ wavefunction\ that includes information on the equilibrium geometry. Based on this analysis, we opt for the Jastrow\ wavefunction\ to calculate energetic and structural properties for parahydrogen, orthodeuterium, and paratritium\ clusters\ of size\ N= 4 - 19, 33. Energetic and structural properties are obtained and compared to earlier work based on Monte Carlo PIGS simulations to study the accuracy of the proposed approach. The new results for paratritium\ clusters\ will serve as benchmark for future studies. This paper provides a detailed, yet general method for optimizing the necessary parameters required for the study of the\ ground state\ of a large variety of systems.

}, author = {Matthew Schmidt and Steve Constable and Christopher Ing and Pierre-Nicholas Roy} }