High-performance computing in atomistic materials science Development and application of high-performance atomistic materials simulations methods, particularly first principles quantum mechanics for extended (bulk and surface) systems. Quantum Electronic Structure Method Development: SeqQuest Principal architect of the QUEST suite of Gaussian-basis density functional theory (DFT) pseudopotential codes developed at Sandia, encompassing both fundamental physics methods and algorithm development, and optimized code implementation and parallelization. Emphasis on methods for supercell calculations of defects in materials, particularly proper treatment of electrostatic boundary conditions for charged and polar species. Multiscale Material Simulations Methods Development Development of physics-based quantum-compatible semi-empirical potentials, integration of "multiscale" atomistic methods into a unified tool set, driven by problem needs. Challenge applications: radiation effects in electronic devices (defects and defect evolution in semiconductors, Si, GaAs, and other III-V's, defect chemistry and aging in bulk silica and at Si-SiO2 interfaces), chalcogenide phase-change materials for electronic memory devices (Ge-Sb-Te compounds), aging of metal hydrides, graphene. General applications areas Chemical and electronic properties of defects in bulk oxides and semiconductors, amorphous materials, surface chemistry and catalysis, structural energetics of surface relaxations and bulk crystal phases. Some past focus areas: Nuclear energy waste forms, chemistry and disposition Methods and models for predicting aging and degradation of nuclear waste forms in engineered repositories (NEAMS), from electronic-atomistic through continuum models. Electrochemistry with fields for battery applications Integrated predictive methods for modeling electrochemistry at electrode-electrolyte interfaces from first principles, coupling density functional theory and solvation models with full rigorous treatment of boundary conditions.