QUANTUM SIMULATION OF CHEMICAL DYNAMICS IN CONDENSED PHASES

来自德克萨斯大学奥斯汀分校的Peter Rossky得到了化学理论、模型和计算方法项目的支持，他的研究重点是理解在原子水平上，当化学变化发生在液体溶液或非结构化固体材料中时，分子排列和随时间变化的过程。这些变化包括发生在生物材料、半导体材料和塑料中的变化。尽管计算建模越来越能够描述这些过程，但严峻的挑战仍然存在。例如，能够理解通过吸收光而沉积在分子中的能量发生了什么是非常重要的。这些知识对于我们理解材料的降解、太阳能电池的功能以及光合作用等生物过程至关重要。目前研究的具体目标是发展新的、普遍适用的、理论和计算模型和方法，这些模型和方法可以完全描述涉及非常轻的原子和电子的化学，在这些化学中必须调用量子力学。正在开发的算法可以直接应用于先进材料设计、药物发现和纳米工程的计算工具。它们还可以影响关键的实际问题，包括可负担得起的可持续能源和可持续气候的太阳能捕获。这项工作产生的外联活动有助于未来科学工作队伍的稳定，以及公众参与科学政策的能力。研究工作正在为核运动的量子力学描述开发新的模拟算法，这些算法在关键方面超越了目前可用的实用方法。这种新方法基于Wigner变换变量的动力学，是早期线性化路径积分（“经典Wigner”）方法的直接推广。新方法保留了直接评估非线性算符动力学的能力（例如，在非弹性x射线散射中），并在没有与模拟算法相关的非物理成分的情况下描述振动动力学。此外，由于新方法直接传播相空间点（与基于路径积分的方法相反），因此有充分的理由相信它可以集成到非绝热电子动力学协议中。应用于相对较好表征的分子系统被用来测试新方法的能力。引导我们找到具有所需功能的新材料或洞察自然解决方案所需的分子尺度洞察力，将遵循先进计算科学的实施，与揭示性实验探针相协调。由此产生的能力构成了未来可能成为常规建模方法的基础，就像过去50年的基础研究为今天的实验研究人员提供的常规一样。项目努力加强了各级教育，包括研究生和博士后的专业发展，使他们成为具有计算解决物理问题的及时技能的研究人员和教育工作者。

Peter Rossky from the University of Texas at Austin is supported by the Chemical Theory, Models and Computational Methods Program in research focused on understanding, at the level of atoms, the molecular arrangements and time-dependent processes that occur when chemical changes take place in liquid solutions or in unstructured solid materials. These include the changes that occur in biological materials, in semiconductor materials, and in plastics. Although computational modeling is increasingly able to describe these processes, serious challenges remain. For example, it is very important to be able to understand what happens to the energy that is deposited in molecules through the absorption of light. Such knowledge is a critical element for our understanding of the degradation of materials, of the functioning of solar cells, and of biological processes such as photosynthesis. The specific objective of the present studies is the development of new, generally applicable, theoretical and computational models and methods that can fully describe chemistry involving very light atoms and electrons, where quantum mechanics must be invoked. The algorithms being developed can be directly applied as computational tools for the design of advanced materials, pharmaceutical discovery, and nanoscale engineering. They can also impact critical practical issues, including affordable solar energy capture for sustainable energy and a sustainable climate. Outreach activities stemming from this work contribute to the future stability of the scientific workforce, as well as to the public's ability to participate in science policy.The research efforts are developing new simulation algorithms for the quantum mechanical description of nuclear motion that go beyond presently available practical methods in key respects. The novel method is based on the dynamics of Wigner transform variables and is a rather direct generalization of an earlier linearized path integral ("classical Wigner") approach. The new approach retains the ability to directly evaluate the dynamics of non-linear operators (e.g., in inelastic X-ray scattering) and describes vibrational dynamics without unphysical components associated with the simulation algorithm. Further, since the new method directly propagates the phase space points (in contrast to path-integral based approaches), there is good reason to believe that it can be integrated into a non-adiabatic electronic dynamics protocol. Applications to relatively well-characterized molecular systems are being used to test the capability of new methods. The molecular-scale insight needed to guide us to new materials with desired functions or insight into Nature's solutions will follow from the implementation of advanced computational science, coordinated with revealing experimental probes. The resulting capabilities form the basis for what may be the routine modeling methods of the future, just as the basic research of the last 50 years routinely provides for today's experimental researcher. Project efforts enhance education at all levels, including the professional development of graduate and postdoctoral students as researchers and educators with timely skills in the computational solution of physical problems.