Theoretical and Computational Studies of Quantum Dynamical Processes in Condensed Matter Systems

Gregory Voth获得了理论与计算化学项目的资助，从事凝聚态系统中量子动力学过程的研究。他将在费曼路径积分公式中使用虚时间路径质心的动力学性质。用质心分子动力学方法计算多体系统的时间位置相关函数。在该方法中，类经典运动方程生成的质心轨迹与相空间费曼路径积分质心密度相关并统计加权。由此得到的相关函数可以通过傅里叶变换与量子位置相关函数相关联。将开发新的算法来求解质心分子动力学方程，并将其应用于许多凝聚态研究，包括：1)液态水中的量子隧道效应和模式量化效应；2)水合电子在量子化水中的扩散输运；3)过量质子在水及相关体系中的量子动力学运动。气相化学系统已经被研究了许多年，并且已经发展了优秀的理论和计算技术来模拟它们的行为。最近正在开发理论和计算方法，使处理更复杂的凝聚相系统成为可能。目前的大多数理论模型本质上都是经典的，无法处理量子效应带来的额外复杂性。Voth的研究解决了这一额外的复杂性，并提出了计算方法的发展，这将允许处理包含各种量子自由度的凝聚相系统。

Gregory Voth is supported by a grant from the Theoretical and Computational Chemistry Program to perform studies of quantum dynamical processes in condensed phase systems. He will employ the dynamical properties of the imaginary time path centroid in the Feynman path integral formulation. The time position correlation function in many-body systems will be computed using centroid molecular dynamics. In this method classical-like equations of motion generate centroid trajectories which are correlated and statistically weighted with the phase space Feynman path integral centroid density. The resulting correlation function can then be related by Fourier transform to the quantum position correlation function. New algorithms will be developed to solve the centroid molecular dynamics equations, and they will be applied to a number of condensed phase studies including: 1) quantum tunneling and mode quantization effects in liquid water; 2) diffusive transport of the hydrated electron in quantized water; and 3) the quantum dynamical motion of an excess proton in water and related systems. Gas phase chemical systems have been studied for a number of years, and excellent theoretical and computational techniques have been developed to model their behavior. More recently theoretical and computational methods are being developed which make it possible to treat more complex condensed phase systems. Most of the current theoretical models are classical in nature, and cannot deal with the additional complications imposed by quantum effects. Voth's research addresses this additional degree of complexity, and proposes the development of computational approaches which will permit the treatment of condensed phase systems which include various quantum degrees of freedom.