XVIth International Workshop on
Quantum Systems in
Chemistry and Physics
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Recent Developments in the Electron Nuclear Dynamics Theory:
From Coherent-States and Density-Functional-Theory Implementations to Applications in Cancer Proton Therapy
Jorge A. Morales
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409
Recent developments and applications of the electron nuclear dynamics (END) theory [1] will be presented [2-4]. END is a time-dependent, variational, non-adiabatic method for chemical dynamics that evaluates potential energy and interatomic forces “on the fly”, without employing predetermined potential energy surfaces. The simplest-level END (SLEND) [1] adopts a nuclear classical-mechanics description (as the zero-width limit of frozen Gaussian wave packets) and an electronic single-determinantal wavefunction. In the SLEND framework, three new developments will be presented:

1. The use of various types of coherent-states (CS) sets [4] to describe all types of particles (nuclei and electrons) and of degrees of freedom (translational, rotational [5], vibrational [6], and electronic). The CS sets conveniently represent the SLEND trial wavefunction and can mediate between classical and quantum descriptions. For instance, the rotational [5] and canonical [6] CS sets permit reconstructing rovibrational quantum properties from the SLEND nuclear classical dynamics. Conversely, a new CS set [2] participates in a valence-bond approach to a classical-electrostatics/charge-equilibration model based on the Sanderson principle of electronegativity equalization.

2. A new time-dependent Kohn-Sham density-functional-theory (KSDFT) method in the SLEND framework: END/KSDFT [3], which incorporates electron correlation effects absent in SLEND.

3. A new implementation of effective core potentials into SLEND and END/KSDT to treat large systems.

The new developments are implemented in our code: PACE (Python Accelerated Coherent-states Electron-nuclear dynamics) that utilizes several computer-science technologies [code parallelization, compute unified devise architecture (CUDA) devices, etc.]. The new developments are applied to the following chemical systems:

1. High-energy collisions of protons with water clusters (water radiolysis) and with DNA components (direct DNA damage): these processes are highly relevant to proton cancer therapy.

2. Various proton-molecule reactions [7,8] with an emphasis on accurately predicting rovibrational, energy-transfer, and electron-transfer properties.

3. Various chemical reactions involving large reactants, such as Diels-Alder and SN2 reactions inter alia.

Results of the above simulations compare well with available experimental results.

[1] E. Deumens, A. Diz, R. Longo, Y. Öhrn, Rev. Mod. Phys. 66 (1994) 917.
[2] J. A. Morales, J. Phys. Chem. A 113 (2009) 6004.
[3] S. A. Perera, P. M. McLaurin, T. V. Grimes, J. A. Morales, Chem. Phys. Lett. 496 (2010) 188.
[4] J. A. Morales, Mol. Phys. 108, 3199 (2010)
[5] J. A. Morales, E. Deumens, Y. Öhrn, J. Math. Phys. 40 (1999) 766.
[6] J. A. Morales, A. Diz, E. Deumens, Y. Öhrn, J. Chem. Phys. 133 (1995) 9968.
[7] B. Maiti, R. Sadeghi, A. Austin, J. A. Morales, Chem. Phys. 340 (2007) 105.
[8] B. Maiti, P. M. McLaurin, R. Sadeghi, S. A. Perera, J. A. Morales, Int. J. Quant. Chem. 109 (2009) 3026.

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