Theoretical and Computational Studies of Quantum Dynamical Processes in Condensed Matter

Gregory A.犹他州大学的Voth得到了理论和计算化学项目的支持，对激发态反应动力学、表面化学和凝聚相过程进行理论研究。目前的重点是扩展和进一步发展质心分子动力学方法（CMD）。CMD方法基于 用经典的分子动力学技术计算费曼路径积分质心的轨迹。 然后将轨迹与相空间费曼路径积分质心密度进行相关和统计加权。 所得到的时间相关函数可以与 通过傅里叶变换到量子时间相关函数。 因此，CMD允许量子时间相关函数近似计算与经典MD计算类似的数值努力。 这种方法的目的是了解质子在水环境中的运输和水合电子的模拟。 正在制定的具体改进措施包括：（1）发展了一种数值精确算法来修正CMD动力学，（2）在质心动力学传播中引入了半经典初值表示，（3）使用高斯表示简化了CMD方法，包括电子自由度的非绝热动力学，（4）引入了非线性相关函数，复杂凝聚相系统中的质子转移是许多生物过程的基本方面，如植物的光合作用和动物的呼吸。对这些过程的完整理解目前尚不存在，需要复杂的理论处理，这些理论处理能够解释电子的量子力学行为和质子的近经典运动。 这里开发的方法非常适合与近经典质子转移的动力学描述。 进一步了解这些过程是必要的仿生材料的太阳能转换，碳封存和可能的生物启发的环境友好催化的发展。 类似的动力学是感兴趣的大气化学，因为质子化的水团在高层大气中是丰富的。 还通过培训本科生和研究生研究人员向各社区传授研究成果。

Professor Gregory A. Voth, of the University of Utah, is supported by the Theoretical and Computational Chemistry Program to perform theoretical studies on excited-state reaction dynamics, surface chemistry and condensed-phase processes. Current focus is on extending and further developing the centroid molecular dynamics method (CMD). The CMD method is based on computing trajectories of Feynman path integral centroids using classical molecular dynamics techniques. The trajectories are then correlated and statistically weighted with the phase space Feynman path integral centroid density. The resulting time correlation function can be related by Fourier transform to the quantum time correlation function. CMD therefore allows quantum time correlation functions to be approximately calculated with a numerical effort similar to a classical MD calculations. Such methods are aimed at understanding proton transport in aqueous environments and in the simulation of hydrated electrons. Specific improvements under development include: (1) the development of a numerically exact algorithm to provide corrections to the CMD dynamics, (2) the incorporation of the semiclassical initial value representation for centroid dynamics propagation, (3) simplifying the CMD approach using Gaussian representations, including nonadiabatic dynamics of the electronic degrees of freedom, (4) inclusion of nonlinear correlation functions, and (5) inclusion of Fermi-Dirac statistics.Proton transfer in complex condensed phase systems is a fundamental aspect of many biological processes such as photosynthesis in plants and breathing in animals. The complete understanding of these processes is currently absent and in need of sophisticated theoretical treatments that are capable of accounting for the quantum-mechanical behavior of electrons and the nearly classical motion of protons. Methods developed here are well suited for dynamical descriptions associated with nearly classical proton transfer. Further understanding of these processes is requisite to the development of biomimetic materials for solar energy conversion, carbon sequestration and possibly biologically inspired environmentally friendly catalysis. Similar dynamics are of interest to atmospheric chemistry since protonated water clusters are abundant in the upper atmosphere. Research is also imparted to various communities through the training of graduate and postgraduate researchers.