Nonadiabatic Molecular Dynamics in Condensed Systems

David Coker得到了理论和计算化学计划的资助，继续他在凝聚系统中非绝热分子动力学的研究。科克正在将非绝热开关理论和表面跳跃理论结合起来，研究量子和经典子系统之间的能量再分配。这为处理凝聚相系统中的非绝热动力学提供了一种新的方法。另外一些新的方法将被开发用于在存在经典浴自由度的情况下模拟具有很少非绝热量子自由度的系统。探索核非绝热的应用包括：1)研究溶剂密度对氢分子在溶液中的非绝热转动动力学的影响及其对旋转喇曼线宽的影响；2)非绝热动力学和隧穿对氢分子在冰中输运的影响；3)研究溶液中分子间的质子转移反应，以及溶剂极化和平面性对质子动力学的隧穿和非绝热的影响。通过引入半经验价键方法来研究溶液反应中的电子非绝热性，这种方法被称为分子中的硅原子学。该方法将用于研究双原子碘、双原子碘阴离子和甲基碘在不同分子溶剂中光激发后的早期非绝热动力学。由于大多数工业合成过程都是在溶液中进行的，因此重要的是要更好地了解溶剂对溶剂化体系中基本化学过程的影响，包括分子传输、质子转移和电子激发。这一理论研究将有助于更好地理解溶液中化学反应的影响因素。

David Coker is supported by a grant from the Theoretical and Computational Chemistry Program to continue his research in nonadiabatic molecular dynamics in condensed systems. Coker is combining nonadiabatic switching formalism with surface hopping theory to study energy redistribution between quantum and classical subsystems. This has resulted in a new approach for treating nonadiabatic dynamics in condensed phase systems. Additional new methods will be developed for simulating systems with few nonadiabatic quantum degrees of freedom in the presence of a classical bath degrees of freedom. Applications which explore nuclear nonadiabaticity include: 1) studies of the effects of solvent density on the nonadiabatic rotational dynamics of hydrogen molecule in solution and the influence they have on rotational Raman linewidths; 2) the influence of nonadiabatic dynamics and tunneling on transport of hydrogen molecule in ice; and 3) studies of solution phase intermolecular proton transfer reactions and the effects of solvent polarization and planarity on tunneling and nonadiabaticity of proton dynamics. Electronic nonadiabaticity in solution phase reactions will be studied by the introduction of a semi-empirical valence bond approach called diatomics in molecules. This approach will be used to study early time nonadiabatic dynamics after photoexcitation of diatomic iodine, diatomic iodine anion, and methyl iodide in various molecular solvents. Since most industrial synthetic processes occur in solution, it is important to gain an increased understanding of the influence which solvent has on fundamental chemical processes in solvated systems including molecular transport, proton transfer, and electronic excitation. This theoretical research will lead to an improved understanding of the factors which influence chemical reactions in solution.