Predictive electronic structure calculations are at the core of materials modeling.

1. Quantum simulations of correlated materials Shiwei Zhang, College of William and Mary, DMR 1006217 Predictive electronic structure calculations are at the core of materials modeling. We have developed an auxiliary-field quantum Monte Carlo (AFQMC) approach to better treat electron interaction effects. AFQMC takes the form of random walks in an abstract mean-field space, and can be “easily” built on top of standard machineries in condensed matter and chemistry to improve accuracy. We apply the method to both model systems and real materials. (Cover figure of J. of Phys. Cond Matt. Dec 21, 2011 issue) Long-wavelength collective modes of spin-density waves in the two-dimensional Hubbard model. Shown are the charge and spin densities in a 36x36 lattice versus interaction strengths. For technical descriptions, see publications athttp://physics.wm.edu/~shiwei Collaborators: S. Chiesa, H. Krakauer, F.J. Ma, W. Purwanto, H. Shi, E.J. Walter, Y. Virgus, J.Xu

2. Quantum simulations of correlated materials Shiwei Zhang, College of William and Mary, DMR 1006217 • PI was lecturer at the School on “Quantum Monte Carlo methods at work for novel phases of matter” held at the ICTP in Trieste: • http://www.democritos.it/montecarlo2012/index.php/Main/HomePage • with over 100 participants from around the world • Developed Matlab AFQMC program suite (with grad student Dorothy Xu and REU student Huy Nguyen) to help train others --- code was used at Winter School for one of the lab sessions and then made publicly available Undergraduate student Huy Nguyen (REU student from Reed College) explains a pedagogical Matlab module we developed to help learn QMC methods. Graduate student Hao Shi and PI lead a hands-on Lab session on AFQMC at an international winter-school in Trieste, Italy (Jan 2012).