Associate Professor of Chemistry
Ph.D. Wayne State University, 2003
Research in the Li group focuses on developing and applying electronic structure theories and ab initio molecular dynamics for studying properties and reactions, in particular non-adiabatic reactions that take place in large systems, such as polymers, biomolecules, and clusters. Students will have a unique opportunity to participate in interdisciplinary research subjects.
The Born-Oppenheimer (BO) and extended Lagrangian (EL) trajectories are founded on the assumption that a single electronic potential surface governs the dynamics. Such adiabatic approaches are widely used in investigations of reactions on ground state surfaces. A major limitation of adiabatic trajectories is that they are not applicable to reactions involving nonadiabatic electronic processes, i.e., multiple potential energy surfaces. Proper incorporation of the electronic response is crucial for describing a host of dynamical processes, including laser induced chemistry, dynamics at metal or semiconductor surfaces, and electron transfer in molecular, biological, interfacial, or electrochemical systems. Recently, we introduced an efficient ab initio direct Ehrenfest dynamics algorithm within the TDHF and TDDFT approximations (J. Chem. Phys., 2005, 123: 084106). This approach integrates ab initio TDHF/TDDFT equation "on the fly." Electron dynamics is described within a non-adiabatic non-perturbative framework.
Geometry optimization is an essential part of computational chemistry. Any theoretical investigation that involves calculations of transition structures, barrier heights, heats of reaction, or vibrational spectra requires searches for one or more minima or saddle points on a potential energy surface (PES). Computational methods are applied to large systems of ever increasing size. Biomolecules, polymers and nanostructures with hundreds to thousands of atoms are often difficult to optimize because of excessive degrees of freedom. Any decrease in the computational cost and increase in the general stability of geometry optimization would be welcome. We are interested in developments of efficient optimization methods for both electron wave function and nuclear geometry. Our developments span from novel two electron integration methods and energy minimization schemes to advanced computer machinery including high performance parallelism and cost effective sparse matrix manipulations.
Our theoretical developments are being applied to studies of laser controls of molecular reactions, electron transfer at surfaces, nonadiabatic reactions in biological systems, and characterizations of magnetism in nanoparticles.
E. Badaeva, J. W. May, J. Ma, D. R. Gamelin, X. Li, “Characterizations of Excited-state Magnetic Exchange in Mn2+-doped ZnO Quantum Dots using Time-Dependent Density Functional Theory,” J. Phys. Chem. C, 2011, 115, 20986.
W. Liang, X. Li, L. R. Dalton, B. H. Robinson, B. E. Eichinger, “Solvents Level Dipole Moments,” J. Phys. Chem. B, 2011, 115, 12566.
W. Liang, S. A. Fischer, M. J. Frisch, X. Li, “Energy-specific linear response TDHF/TDDFT for calculating high-energy excited states,” J. Chem. Theory Comput., 2011, 7, 3540.
F. Ding, W. Liang, C. T. Chapman, X. Li, “On the Gauge Invariance of the Time-dependent Hartree-Fock and Kohn-Sham Electronic Dynamic,” J. Chem. Phys., 2011, 135, 164101.
S. A. Fischer, C. T. Chapman, X. Li, “Surface Hopping with Ehrenfest Excited Potential,” J. Chem. Phys., 2011, 135, 144102.
C. T. Chapman, W. Liang, X. Li, “Ultrafast Coherent Electron-hole Separation Dynamics in a Fullerene Derivative,” J. Phys. Chem. Lett., 2011, 2, 1189.
W. Liang, C. T. Chapman, X. Li, “Efficient First-Principles Electronic Dynamics,” J. Chem. Phys., 2011, 134, 184102.
D. H. Bale, B. E. Eichinger, W. Liang, X. Li, L. R. Dalton, B. H. Robinson, P. J. Reid, “Dielectric Dependence of the First Molecular Hyperpolarizability for Electro-Optic Chromophores,” J. Phys. Chem. B. 2011, 115, 3505.
C. T. Chapman, W. Liang, X. Li, “Open-system Electronic Dynamics and Thermalized Electronic Structure,” J. Chem. Phys. 2011, 134, 024118.
Sloan Research Fellowship 2011
National Science Foundation Career Award 2009
NSF CAREER Award, 2009
UW Royalty Research Fund Award, 2006
Graduate Dissertation Fellowship, Wayne State University, 2003
Dan Trivich Memorial Award, Wayne State University, 2003
Thomas C. Rumble Fellowship, Wayne State University, 2002
Outstanding Student Leadership Award, University of Science and Technology of China, 1998
National Award for Major Scientific and Technological Contributions, the Bureau of Education, China, 1997