Theoretical Studies of Non-Valence Correlation-Bound Anions and of Positron-Molecule Complexes

匹兹堡大学的肯尼斯·乔丹得到了化学系化学理论、模型和计算方法项目的支持，他开发了研究额外电子与分子和分子簇结合的计算方法。将电子从一个位置转移到另一个位置是光合作用、晶体管操作和腐蚀等各种过程的关键。尽管过剩电子在生物、化学和物理中很重要，但它们如何与周围环境相互作用仍然没有被很好地理解。乔丹教授和他的同事开发并应用了新的计算方法来精确地表征分子之间以及分子与表面的相互作用。该项目为年轻的研究人员(学生和博士后研究员)提供计算机建模领域的培训。这个项目的目标是详细了解分子和团簇结合过剩电子和正电子时，静电学和长程关联效应的相对重要性。由于扩散蒙特卡罗方法在高度并行的计算机系统上的可扩展性和给出精确相互作用能的潜力，扩散蒙特卡罗方法正越来越多地被应用于化学问题。然而，扩散蒙特卡罗方法需要使用试探波函数来确定节面，并且对相关误差的大小知之甚少。这项研究项目旨在解决这一问题，特别强调建立试验函数的灵活性，以准确预测水与多环芳烃的相互作用能，目标是外推到石墨烯的极限。这些项目非常适合为参与的学生和博士后研究人员提供理论化学和计算机模拟方面的广泛背景。这是劳动力中非常需要的一套技能。计划努力招募更多的本科生，特别是妇女和代表性不足的少数群体成员。

Kenneth Jordan, of the University of Pittsburg is supported by an award from the Chemical Theory, Models and Computational Method program in the Chemistry division to develop computational approaches for studying the binding of extra electrons to molecules and clusters of molecules. Moving electrons from one location to another is the key to processes as diverse as photosynthesis, the operation of transistors, and corrosion. In spite of the importance of excess electrons in biology, chemistry, and physics, how they interact with their surroundings is still not well understood. Professor Jordan and coworkers develop and apply new computational methods to accurately characterize interactions between molecules and of molecules with surfaces. The project provides training of young researchers (students and postdoctoral fellows) in the area of computer modeling. The goal of this project is to provide a detailed understanding of the relative importance of electrostatics and long-range correlation effects in the binding of excess electrons and positrons by molecules and clusters. Due to its scalability on highly parallel computer systems and its potential for giving accurate interaction energies, the diffusion Monte Carlo method is being increasingly applied to chemical problems. However, the diffusion Monte Carlo method requires the use of a trial wave function to fix the nodal surface, and little is known about the magnitude of the associated errors. This research project is designed to address this problem, with particular emphasis on establishing the flexibility in the trial functions for accurate prediction of interaction energies of water with polycyclic aromatic hydrocarbons, with the goal of extrapolating to the graphene limit. The projects are ideally suited to provide the participating students and postdoctoral researchers a broad background in theoretical chemistry and computer simulations. This is a skill set that is in high demand in the workforce. Efforts are planned to recruit more undergraduates, especially women and members of underrepresented minorities, into the group.