Abstract:
I will briefly introduce quantum Monte Carlo (QMC) methods for calculations of electronic structure. QMC combines physical and mathematical insights about quantum many-body effects with stochastic simulation techniques and enables us to solve the stationary Schrodinger equation with high accuracy and computational efficiency. The method has been applied to variety of systems such as molecules, clusters and solids with up to a few hundreds of valence electrons and typically provides about 95% of the electron-electron correlation energy. QMC estimations of quantities such as cohesions, band gaps, energy differences between different structures, etc, and agree with experiments within a few percent. I will also mention effort to reach beyond the only fundamental approximation involved, which has to do with avoiding the fermion sign problem, such as analysis of nodes of fermion wavefunctions and new types of trial wavefunctions based on pfaffians rather than Slater determinants and very recent progress in on-the-fly evaluation of electronic energies and forces in molecular dynamics simulations, ie, the development of a QMC/MD method.

* in collaboration with L.K. Wagner, M. Bajdich, G. Drobny, K.E Schmidt (Arizona State U.), J.C. Grossman (UC Berkeley).