Full-Response TDDFT on Graphical Processing Units for Modeling Optical Response in Materials

Limited computational resources remain a serious obstacle to the application of quantum chemistry in problems of widespread importance, such as the design of new catalysts for use in fuel cells, or for modeling of material and optical properties of liquids and solids. Researchers have a considerable impetus to relieve this bottleneck, both by developing new and more effective algorithms and exploring new computer architectures. Research at Stanford has yielded a working quantum chemistry code for graphical processing units (GPUs) that calculates electronic ground states of systems as large as 2000 atoms using the DFT method. We propose to extend this work to allow calculations of the full optical response of materials using real-time (RT) TDDFT with periodic boundary conditions (PBCs). Our Phase I approach consists of two tasks. First, we will validate our approach for condensed phase problems of interest to the Air Force using existing codes. Secondly, we will derive algorithms for RT-TDDFT method and for PBCs that are suitable for GPU implementation. At the end of our phase II project, we plan to deliver a RT-TDDFT code that can be used with PBCs and that executes on the highly efficient, highly scalable GPU platform. BENEFIT: The product of the proposed STTR effort, after Phase II, is a computer software module that would allow for the efficient and accurate prediction of the linear and non-linear optical response of materials. The software, which will be designed to run on graphical processing units, will permit efficient, thousand-atom simulations using the high-level real-time TDDFT method and periodic boundary conditions. These simulations will 2-3 times faster and 10 times bigger than those performed by current software on standard CPU platforms. The Phase I proof-of-principle demonstration will consist of a test of full-response function, real-time (RT) TDDFT for its applicability to Air Force problems and the derivation of the mathematical algorithms for RT-TDDFT with periodic boundary conditions. This new simulation software will enable modeling of the complex interaction of light and matter in photovoltaic materials and non-linear optical devices, as well the UV/Vis absorption spectra of chemical and biological agents, explosives for better detection techniques.