Theory of Chemical Dynamics

加州大学伯克利分校的威廉·米勒得到了化学理论、模型和计算方法计划的支持，该计划探索新的半经典初值表示方法来处理电子非绝热过程，即涉及几个势能面(电子态)上的分子动力学的过程。振动哈密顿量的Meyer-Miller-Stock-Thoss表示为实现这一点提供了一种公认的方法，并寻求在此框架内进行计算的更有效的方法。一种更雄心勃勃但不太成熟的方法显示了巨大的前景，它在更基本的水平上引入了对电子自由度的经典描述，即单个费米子态的创建/湮灭算符。人们正在研究这一公式，以了解它所展示的最初非常有希望的性能是否能更普遍地保持下去。电子非绝热过程奠定了一些应用的基础，这些应用对许多当前重要的技术至关重要。这包括在无机纳米材料和光合作用系统中与太阳能到电能转换有关的光伏过程，以及“分子电子学”领域，例如，电子通过作为电极之间连接的各种分子结构的传输。理论描述的发展使人们能够在经典分子动力学模拟方法的框架内处理非绝热过程，这将使对更现实的分子模型进行此类计算成为可能，从而与这些领域的实验工作更有成效地相互作用。

William Miller of the University of California, Berkeley is supported by an award from the Chemical Theory, Models and Computational Methods program to explore new semiclassical initial value representation approaches for treating electronically non-adiabatic processes, i.e., those involving molecular dynamics on several potential energy surfaces (electronic states). The Meyer-Miller-Stock-Thoss representation of the vibronic Hamiltonian provides one well-established way for doing this, and more efficient ways of carrying out calculations within this framework are pursued. A more ambitious but less well established approach, that shows great promise, introduces the classical description of the electronic degrees of freedom at a more fundamental level, that of the creation/annihilation operators of the individual fermionic states. This formulation is being pursued to see if the initial very promising performance it has demonstrated is maintained more generally.Electronically non-adiabatic processes underlie a number of applications that are crucial for many technologies of current importance. These include photo-voltaic processes relevant to solar-to-electric energy conversion, in both inorganic nano-materials and in photosynthetic systems, and the field of "molecular electronics", e.g., the transmission of electrons through various molecular structures that are junctions between electrodes. Development of theoretical descriptions that allow one to treat non-adiabatic processes within the framework of classical molecular dynamics simulation methodology will make it feasible to carry out such calculations for much more realistic molecular models and thus interact more fruitfully with experimental work in these areas.