Research Statement:
I have been focusing my attention on Quantum Monte Carlo (QMC) and Density Functional Theory (DFT) simulations of solids. Specifically, I've been computing properties of defects in silicon, high pressure silicate phases, and magnetic transitions in transition metal oxides using massively-parallel computer systems. Methodologically, I'm interested in developing QMC techniques, trying to understand discrepancies between QMC and DFT, and identifying accurate exchange-correlation functionals for solids. Understanding silicon defects and finding accurate methods to model them is important because they ultimately hinder the fabrication and efficiency of semiconductor devices, such as computer chips. Silicates (silica and magnesium silicate) are the most common minerals found in Earth's mantle, and, yet, their phase diagram and elastic properties are often not very well constrained at high pressures. I have been computing phase transitions, equations of state, and elastic properties of high pressure mineral phases to help further constrain seismic and experimental data.

Grants written/co-authored

Computer time
NERSC 2008 Renewal, 1 million CPU hours
NERSC 2009 Renewal, 3 million CPU hours
NERSC 2010 Renewal, 3.5 million CPU hours
OSC 2006 Renewal, 330 thousand CPU hours
OSC 2007 Renewal, 390 thousand CPU hours
OSC 2008 Renewal, 1.4 million CPU hours
OSC 2010 Renewal, 3.8 million CPU hours

Funding
DOE-BES-DMS Renewal 2008

Silica Phases Under Pressure

Silicon Defects

Magnesium Silicate Phase Transitions

pdf image

Manganese Oxide Spin Transition

Figure from C.S Yoo PRL, 92, 115502 (2005).