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45420-AC6
Combined Coherent-States/Density-Functional-Theory Dynamics

Jorge A. Morales, Texas Tech University

This project involves the development of an ab initio molecular dynamics method that combines coherent states (CS) and density functional theory (DFT) capabilities. In this dual approach, the CS theory supplies suitable over-complete sets to represent wave functions and express quantum dynamical equations in a classical-like format; reciprocally, DFT supplies an adequate description of electron correlation effects at low computational cost. In the resulting method, nuclei are described by a product of narrow, frozen Gaussian wave packets, which is separable into translational, rotational, and vibrational quasi-classical CS factors, whereas electrons are described by a single-determinantal Thouless CS in a Kohn-Sham fashion. This method improves some features of the celebrated Car-Parrinello method by providing: (a) an ab initio CS Lagrangian, (b) a quasi-classical CS description of chemical reaction properties at final time, and (c) a non-redundant representation of an electronic single-determinantal state.

During the second year of this project, our research efforts concentrated on four aspects of this approach:

(1) We further developed and published the above described CS approach to chemical dynamics in terms of several types of CS sets for all type of particles (nuclei and electrons) and for all classes of degrees of freedom (translational, rotational, vibrational; electronic).

(2) We continued implementing the CS/DFT method into our program CSTechG. CSTechG is developed from the ENDyne 2.7-2.8 program (E. Deumens, 1997), of the germane electron nuclear dynamics (END) theory, and from available DFT codes. Significant aspects in this lengthy implementation include: (a) the formulation and programming of single-determinantal Thouless CS capabilities within a DFT/Kohn-Sham context; and (b) the programming of numerous CS/DFT libraries and interfaces to extend conventional DFT capabilities to a CS dynamics context. Ongoing efforts concentrate on the thorough testing of the coded CS/DFT capabilities, both at the time-independent (initial/final states; tests completed) and the time-dependent (dynamics; tests ongoing) levels. The CSTechG implementation and testing will be completed during the one-year extension of this project.

(3) We continued implementing and applying the CS capability to evaluate chemical reaction properties (e.g. differential and integral cross sections) from the final states of simulated dynamics. This CS capability utilizes the above-mentioned CS factorization to analyze and resolve the calculated properties into rotational, vibrational and electronic states. Preliminary applications of this CS procedure were conducted on the final states of END simulations of the following reactions at E_Lab = 30 eV: H⁺ + HF, H⁺ + CO₂ and H⁺ + C₂H₄.

(4) In collaboration with the Texas Tech University (TTU) High Performance Computer Center, we continued developing a compute grid implementation of the proposed CS/DFT dynamics on the TTU compute grid (TechGrid) and the Texas Internet Grid for Education and Research (Tigre). With this powerful technology, several trajectory calculations to simulate a given chemical reaction can be efficiently initialized, run in parallel, and analyzed by utilizing all the available compute nodes in the mentioned grids. This compute grid application will be used for research and scientific training of TTU students.

The present project involved the training and education of: one postdoctoral associate, one chemistry graduate student, and three chemistry undergraduate students (the three being female Hispanic students). In addition, the developed codes were employed as educational tools during the Summer Research Academy in Theoretical and Computational Chemistry (SRATCC) 2008. SRATCC 2008 was conducted in the Department of Chemistry and Biochemistry at Texas Tech University from June 16 to July 11, 2008. The PI of this grant was the main organizer of this program in collaboration with other professors in the department. SRATCC encourages broadening participation in theoretical and computational chemistry research for local high school students and teachers, especially from the Hispanic community. This year, five students and one teacher were chosen from Estacado High School, Lubbock, Texas, to work alongside the participating professors on research projects supported by the American Chemical Society Petroleum Research Fund, the National Science Foundation, and The Welch Foundation. The high school participants presented the results of their research in a public session in the Department of Chemistry and Biochemistry on July 10, 2008, followed by a closing dinner. The CS/DFT codes developed with this grant were used for the education of the high school teacher and one high school student in the SRATCC 2008.

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