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45420-AC6
Combined Coherent-States/Density-Functional-Theory Dynamics
This project involves the development of an ab initio molecular dynamics method that combines coherent states (CS) and density functional theory (DFT) capabilities [Chem. Phys. Lett. 420, 54 (2006)]. In this dual approach, 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 approximately 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: an ab initio CS Lagrangian, a quasi-classical CS description of chemical reaction properties at final time, and a non-redundant representation of an electronic single-determinantal state.
During the first year of this project, our research efforts concentrated on three closely related aspects of the proposed approach:
(1) We began the code implementation of the described methodology into the program CSTechG, starting from the ENDyne 2.7-2.8 program (Deumens, 1997) of the germane electron nuclear dynamics (END) theory and from different public-domain DFT codes. Significant aspects in that lengthy implementation include: (a) the formulation and programming of single-determinantal Thouless CS capabilities within a DFT Kohn-Sham context; (b) the implementation of numerous CS/DFT libraries to extend conventional DFT capabilities to a CS dynamics context. The current version of CSTechG is being tested for the simulation of intramolecular processes and proton-molecule reactions [Chem. Phys. Lett. 420, 54 (2006)].
(2) We began implementing and testing an associated 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 degrees of freedom. Preliminary applications of that CS procedure were conducted on final states of END simulations of the reactive systems: H+ + HF [Chemical Physics, in press (2007)], H+ + CO2, and H+ + NO at ELab = 30 eV .
(3) In collaboration with the Texas Tech University (TTU) High Performance Computer Center (HPCC), we began 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.
