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During the grant period of 09/01/2008-08/31/2009, our research supported by the ACS-PRF-G award has been extremely fruitful in scientific merits and promoting multi-disciplinary graduate education. During this period of time, we have published five articles with additional one submitted. We now have a non-adiabatic non-perturbative method that is able to obtain some important aspects of laser control of molecular reactions and electronic behaviors in quantum particles.

1. Moss, Christopher; LI, XIAOSONG "First order simultaneous optimization of molecular geometry and electronic wave function" Journal of Chemical Physics, 2008, 129, (11), 114102. We present a very efficient simultaneous optimization method for both molecular geometry and electron wave function. We introduce a simultaneous least squares scheme to minimize errors in a full local quadratic space of both geometric and wave function vectors. Several self-consistent-field iterations are taken until a uniform search direction is achieved in every geometry optimization step. Not only does this new simultaneous optimization method significantly reduce the number of self-consistent-field iterations to reach convergence, it is able to overcome shallow potential wells to find a better stationary point. This new method exhibits up to ~60% savings in computational cost compared to conventional geometry optimization methods.

2. LI, XIAOSONG; Moss, Christopher; Liang, Wenkel; Yong, Feng "Car–Parrinello density matrix search with a first principles fictitious electron mass method for electronic wave function optimization" Journal of Chemical Physics, 2009, 130, (23), 234115. We introduce a first principles fictitious mass scheme to weigh each individual density element differently and instantaneously. As an alternative to diagonalization in SCF, the Car-Parrinello scheme is implemented as a density matrix search (CP-DMS) method. Not only does the fictitious mass scheme developed herein allow a very fast SCF convergence, but also the CP-DMS exhibits linear scaling with respect to the system size for alanine helical chain test molecules. The excellent performance of CP-DMS holds even for very challenging compact three-dimensional quantum particles. While the conventional diagonalization based SCF method has difficulties optimizing electronic wave functions for CdSe quantum dots, CP-DMS shows both smooth and faster convergence.

3. Isborn, Christine M.; LI, XIAOSONG "Singlet-triplet Transitions in Real-time Time-dependent Hartree-Fock/Density Functional Theory" Journal of Chemical Theory and Computation, 2009, 5, (9), 2415–2419. Within real-time TDHF/TDDFT, we present a method that gives the excited state triplet energies starting from a singlet ground state. Using a spin-dependent field, we break the spin-symmetry of the alpha and beta density matrices, which incorporates a triplet contribution into the superposition state. The alpha electron density follows the applied field, and the beta electron density responds to the perturbation from the changing alpha electron density. We examine the individual alpha/beta responses during the electron density propagation. Singlet-triplet transitions appear as ‘dark' states: they are present in the alpha/beta responses but are absent from the total electron density response.

4. Moss, Christopher; Isborn, Christine M.; LI, XIAOSONG "Ehrenfest dynamics with a time-dependent density-functional-theory calculation of lifetimes and resonant widths of charge-transfer states of Li+ near an aluminum cluster surface" Physical Review A, 2009, 80, (2), 024503. We present a time-dependent density functional theory (TDDFT) Ehrenfest dynamics approach to study the lifetime and charge neutralization rate of a lithium ion near an aluminum cluster surface. The lifetime of the excited state as a function of surface-atom distance can be determined, including the effects of level crossings, without prior quantitative information about the coupling between atomic levels and surface states. This method can be used to compute lifetimes of excited atomic states near a surface in both the weak- and strong-coupling region, and in the avoided crossing region. Because TDDFT Ehrenfest dynamics is a mean field theory, the wave function consists of contributions from several different excited states during the time propagation. The shortest lifetime is predicted near the region of the avoided crossing between the Li+/Al and Li/Al+ states.

5. Liang, Wenkel; Isborn, Christine M.; LI, XIAOSONG "Laser-Controlled Dissociation of C2H22+ : Ehrenfest Dynamics Using Time-Dependent Density Functional Theory" Journal of Physical Chemistry A, 2009, 113, (15), 3463-3469. Intense laser field dissociations of the acetylene dication are studied by an ab initio Ehrenfest dynamics method with time-dependent density functional theory (TDDFT). Various field frequencies (9.5eV~13.6eV) and field directions are applied to a Boltzmann ensemble of acetylene dication molecules. With the laser field perpendicular to the molecular axis, four fragmentation channels are observed at high frequency with no dominant pathway. With the field parallel to the molecular axis, fragmentations occur at all frequencies and the amount of C-H bond breakage increases with laser frequency. Selective dissociation pattern are observed with low frequency fields parallel to the molecular axis. A systematic analysis of excited state potential energy surfaces is used to rationalize the simulation results.

6. Liang, Wenkel; Isborn, Christine M.; LI, XIAOSONG "Obtaining Hatree-Fock and Density Functional Theory Doubly Excited States with Car-Parrinello Density Matrix Search" Journal of Chemical Physics, 2009, submitted. The calculation of doubly excited states is one of the major problems plaguing the modern day excited state workhorse methodology of linear response time dependent Hartree-Fock (TDHF) and density function theory (TDDFT). We have previously shown that the use of a resonantly tuned field within real-time TDHF and TDDFT is able to simultaneously excite both the alpha and beta electrons to achieve the two-electron excited states of minimal basis H2 and HeH+. We now extend this method to many electron systems with the use of our Car-Parrinello density matrix search (CP-DMS) with a first principles fictitious mass method for wave function optimization. Real-time TDHF/TDDFT is used during the application of the laser field perturbation, driving the electron density towards the doubly excited state. The CP-DMS method then converges the density to the nearest stationary state. We present these stationary state doubly excited state energies and properties at the Hartree-Fock and density functional theory levels for H2, HeH+, lithium hydride, ethylene and butadiene.