My research involves first-principles calculations, theory, and modeling of structural and electronic properties of condensed matter by using the petaflop computational facilities at RPI’s Center for Computational Innovations (CCI). Research directions are largely clean-energy and electronic-applications driven. In particular, I pioneered first-principles theory of defects in semiconductors in the late eighties and since then I have studied numerous defects, especially those in photovoltaic semiconductors. I pioneered first-principles theory of unconventional coordination chemistry of molecular hydrogen on open metal sites as a possible means to store hydrogen on board. I also have a longtime exposure to the physics and chemistry of semiconductor nanostructures and surfaces. In recent years, I study water splitting, ultrafast phase change memory, topological insulators, Weyl semimetals, nano-catalysis, two-dimensional materials, chalcogenide perovskites, monolayer-thick high-temperature superconductor films, and real-time carrier dynamics. I have published 345 peer-reviewed papers in journals such as Phys. Rev. Lett., Nature Comm., PNAS, JACS, Nano Lett. with over 21,000 total citations (Hirsch Index = 69) by Google Scholar’s count and 15,300 (Hirsch Index = 61) by Web of Science's count.