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

*** 9707202 PULAY理论与计算化学项目支持阿肯色大学PULAY教授的工作，以提高SCF和密度泛函方法的效率：多重fock技术和新的基集。在另一个项目中，提出了局部相关方法的进一步发展：梯度和对远对的简化处理。后者构成了大分子中大部分的电子对。密度泛函理论（DFT）尽管在基态上取得了令人信服的成功，但仍然不能适用于激发态。一个项目将探索从DFT借来的经验相关术语的使用，以及精确交换，来描述激发态和双基。普雷建议使用商用PC部件，建立一个强大的量子化学计算并行计算机系统。拟议系统的价格估计约为使用工作站的可比系统的十分之一。提出了以下几个应用：(1)卟啉的几何、力场和振动谱；(2)系统计算和参数化多肽中作为骨干扭角函数的核磁共振位移；(3)参数化在上述资助下生成的200种有机分子的振动力场；(4)寻找新的稳定分子，如光气环状聚合物和相关分子。该奖项旨在提高分子系统量子力学模拟的效率和准确性。通过允许快速计算确定化学系统和材料的性质，这种模拟可能会在未来导致化学、生物化学和材料科学的根本性创新。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，而且直到最近由于新算法和廉价快速计算机的发展才成为可能。该提案列出了几个项目，如果成功，将提高分子量子计算的效率，或者扩展现有方法的适用性。到激发态。这项工作包括基于商品个人计算机部件的并行计算机的构建。＊＊＊

*** 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. ***