Accurate Nonempirical Density-Functional Methods with Applications

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Quantum chemistry is a highly specialized yet critically important branch of chemical research. The most visible outcomes of the work of quantum chemists are predictive mathematical models and computer programs which are used as tools by thousands of researchers in industry and academia to unravel the intricacies of chemical processes, predict physical properties of matter under normal and extreme conditions, design new materials, and search for molecules with target medicinal properties. Our group is one of those that develop such tools; we specialize in a particular quantum-mechanical technique called density-functional theory (DFT). Over the previous granting period, we have advanced an unconventional approach to DFT in which one directly approximates effective one-electron potentials rather than energy functionals. In the next five years, we will take the potential-based DFT to a new level of accuracy and utility by bridging it with nonempirical wavefunction methods. In particular, we will (1) develop conceptually new methods for constructing exchange-correlation potentials which will enable researchers to devise better density-functional and multiscale methods for use in computer simulations of materials; (2) employ our new tool called the average local electron energy to obtain a better understanding of the relation between chemical structure and properties; (3) explore a special reduced form of the Schrödinger equation to uncover fundamental connections between wavefunction methods and DFT; (4) devise a new density-functional approach for studying time-dependent many-electron phenomena; (5) test new ideas to overcome limitations of existing approximate functionals; (6) construct accurate density functionals from model potentials. Tangible outcomes of the proposed research will include new computational methods for investigation of reaction mechanisms, analysis of quantitative structure-activity relationships, and for applications in materials science, attosecond spectroscopy, and other fields. In terms of highly qualified personnel training, the research will form the basis for 10 graduate and 5 undergraduate theses and will contribute expertise to collaborations across interdisciplinary boundaries.