Development and Application of Quantum Chemical Methods for Molecular Potential Surfaces and Properties

*9707202普雷理论和计算化学计划正在支持阿肯色大学的普雷教授致力于提高自洽会和密度泛函方法的效率：多Fock技术和新的基组。在另一个项目中，提出了局部相关方法的进一步发展：梯度和对距离对的简化处理。后者构成了大分子中的大多数电子对。密度泛函理论(DFT)尽管在基态研究中取得了令人信服的成功，但仍然不适用于激发态。一个项目将探索从DFT借用的经验相关项的使用，以及精确的交换，来描述激发态和二元基。Pulay建议使用商用PC部件建立一个用于量子化学计算的强大并行计算机系统。拟议系统的价格估计约为使用工作站的同类系统的十分之一。提出了几个应用：(1)卟啉的几何构型、力场和振动光谱，(2)作为主链扭角的函数的多肽的核磁共振位移的系统计算和参数化，(3)根据先前的资助产生的200个有机分子的振动力场的参数化，(4)寻找新的稳定分子，如光气及其相关分子的环状聚合物。该奖项旨在提高分子系统量子力学模拟的效率和准确性。这样的模拟很可能在未来导致化学、生物化学和材料科学的根本性创新，因为它允许快速计算确定化学体系和材料的性质。较大分子的量子力学方程的精确解需要非常强大的计算机能力，由于新算法和廉价的快速计算机的发展，直到最近才成为可能。例如，该提案列出了几个项目，如果成功，这些项目将提高分子量子计算的效率，或者扩大现有方法的适用性。到激发的电子态。这项工作包括建造一台基于商用个人计算机部件的并行计算机。***

*** 9707202 PULAY The Theoretical and Computational chemistry program is supporting Prof. Pulay of the University of Arkansas for work to improve the efficiency of SCF and density functional methods: the multi-Fock technique, and novel basis sets. In another project, further development of the local correlation method is proposed: gradients and a simplified treatment of distant pairs. The latter constitute the majority of electron pairs in large molecules. Density functional theory (DFT), in spite of its convincing success for ground states, is still not applicable to excited states. A project uill explore the use of empirical correlation terms, borrowed from DFT, together with exact exchange, to describe excited states and diradicals. Pulay proposes to build a powerful parallel computer system for quantum chemical calculations, using commodity PC parts. The price of the proposed system is estimated to be about a tenth of a comparable system using workstations. Several applications are proposed: (1) geometries, force fields and vibrational spectra of porphyrins, (2) systematic calculation and parameterization of NMR shifts in peptides as functions of the backbone torsional angles, (3) parameterization of the vibrational force fields of 200 organic molecules, generated under the preceding grant, (4) search for novel stable molecules, such as the cyclic polymers of phosgene and related molecules. The effort during this award is aimed at increasing the efficiency and accuracy of quantum mechanical simulation of molecular systems. Such simulations are likely to lead to fundamental innovations in chemistry, biochemistry and materials science in the future, by allowing the rapid computational determination of the properties of chemical systems and materials. Accurate solutions of the quantum mechanical equations for larger molecules requires very much computer power, and has become possible only recently due to the development of new algorithms and inexpensive fast computers. The proposal lists several projects that, if successful, will increase the efficiency of molecular quantum calculations, or extend the applicability of present methods, for example. to excited electronic states. The work includes the construction of a parallel computer, based on commodity personal computer parts. ***