Nonlocal density functional theory of molecules and solids

Temple University, Philadelphia PA

Investigators

Abstract

Jianmin Tao of Temple University is supported by an award from the Chemical Theory, Models and Computational Methods Program in the Chemistry Division to develop and apply theoretical methods to predict the properties of molecules and solids. Dr. Tao's work focuses on the family of theoretical methods known as "Density Functional Theory " (DFT). DFT is widely used in the chemistry community because of its speed and ability to characterize the subtle interactions between electrons that determine the energy, shape and behavior of molecules. However, the exact form of the theory is not known; all existing forms are approximations. The goal of Dr. Tao's work is to improve DFT, so that it can make more accurate predictions. The Tao group is applying their new methods to study the properties of organic materials used in electronic devices and solar cells. They are also studying the accuracy of their new methods for the description of transition-metal-based catalysts. One broader impact of their work is a more general, accurate, and flexible form of DFT that can be applied by chemists worldwide, speeding the development of new molecules. In addition, Dr. Tao is developing a summer workshop on DFT for undergraduates and graduate students in the Philadelphia area that helps inspire students to pursue work in the sciences, thus broadening participation. The accuracy of DFT relies on the approximation for the exchange-correlation energy. Development of the exchange-correlation energy as a functional of the electron density is the main task of this theory. Existing functionals are accurate for many properties, such as bond lengths, lattice constants, and atomization energies, but they are often less accurate for band gaps, weak interactions, and reaction barrier heights. The Tao group is working to develop functionals with high accuracy for a broad range of properties by imposing the exact non-uniform scaling constraint on the Tao-Mo functional, and building electronic nonlocality into the Tao-Mo functional by developing local range-separated or hybrid functionals. They are also testing a functional constructed from a model for dynamic polarizability based on the local energy gap. Development of more accurate DFT methods for a wider class of problems may have broad impacts on chemistry, physics, and materials science. In addition, Dr. Tao promote early in engagement by students in advanced theoretical methods through a summer workshop program. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.