Quantum Mechanical Effects in Complex Systems

明尼苏达大学的Donald Truhlar得到了理论和计算化学计划的支持，以开发模拟化学中复杂反应动力系统的新方法，并将这些方法应用于复杂系统中的化学反应。 两个领域的发展被挑出来：酶催化反应和电子非绝热反应（光化学反应）。 该研究将把量子力学效应纳入系统中，这些系统太大，无法通过蛮力融合量子力学结构和动力学计算来处理，并在电子结构理论和动力学的界面上工作。项目工作包括（1）用于模拟酶/辅酶/底物势能函数的QM/MM方法，（2）用于模拟酶坐标参与催化反应的反应坐标的新方法，（3）电子态非绝热表示的新方法，（4）在耦合态动力学的半经典Escherichfest计算中包括退相干的新方法，（5）耦合势能面拟合的新方法;（6）弱耦合势能面碰撞中稀有事件采样的新方法。一个特别的努力涉及使用实验数据和精确的量子动力学来验证半经典方法的准确性，这些方法旨在以实际的方式适用于复杂系统。这项研究将影响我们对光化学动力学和酶机制的分子水平理解，这反过来将对生物化学和大气化学等领域产生影响。 更广泛的影响包括大力指导学生，以及免费分发可从PI网站访问的计算机代码。

Donald Truhlar of the University of Minnesota is supported by the Theoretical and Computational Chemistry Program to develop new methods for simulating complex, reactive dynamical systems in chemistry, and to apply these methods to chemical reactions in complex systems. Two areas of development are singled out: reactions catalyzed by enzymes and electronically nonadiabatic reactions (photochemical reactions). The research will incorporate quantum mechanical effects in systems that are too large to be treated by brute force converged quantum mechanical structural and dynamical calculations, and work at the interface of electronic structure theory and dynamics. Project efforts include (1) QM/MM methods for modeling enzyme/coenzyme/substrate potential energies functions, (2) new methods for modeling the participation of enzyme coordinates in the reaction coordinate for catalyzed reactions, (3) new methods for diabatic representations of electronic states, (4) new approaches to including decoherence in semiclassical Ehrenfest calculations in coupled-state dynamics, (5) new approaches to fitting coupled potential energy surfaces, and (6) new methods for rare event sampling in collisions of systems with weakly coupled potential energy surfaces. A special effort involves the use of experimental data and accurate quantum dynamics to validate the accuracy of semiclassical methods designed to be applicable in a practical way to complex systems. This research will impact our molecular level understanding of photochemical dynamics and enzyme mechanisms, which in turn will have implications in areas such as biochemistry and atmospheric chemistry. Broader impacts include strong efforts in student mentoring, as well as free distribution of computer codes accessible from the PI's web site.