SBIR Phase I: Gridless Density Functional Calculations

95-61117约翰逊这个小型企业创新研究第一阶段项目将专注于为密度泛函的集成开发分析技术。近年来，密度泛函理论(DFT)已成为量子力学分子研究的一种精确的替代第一原理方法，与传统的相关方法相比，它具有成本效益高的优点。遗憾的是，实际中使用的近似密度泛函是相当复杂的，必须用数值求积来积分。这种基于网格的方法存在固有的困难，这些困难不会出现在所有必要积分都是以解析方式计算的方法中，例如在Hartree-Fock理论中。除非在处理分子格子时非常小心，否则在计算中会出现不希望看到的效果。这些不同的困难可以严格处理，但它们的不当处理是大多数实现中问题的根源。第一阶段可行性研究的目标是开发一种解析可积的密度泛函，它产生与狄拉克泛函类似的理论模型化学。我们将在公司内实现由此产生的泛函的S量子化学计算机程序。一种实用的分析方法将消除上述虚假影响，同时很有可能改善中小型系统的计算时间。通过衡量结果质量和系统效率的大幅提高，商业效益是显而易见的，从而提高了研究生产率和成本效益。

95-61117 Johnson This Small Business Innovation Research Phase I project will focus on the development of analytic techniques for the integration of density functionals. In recent years, Density Functional Theory (DFT) has emerged as an accurate alternative first-principles approach to quantum mechanical molecular investigations, which is cost-effective compared with conventional correlated methods. Unfortunately, the approximate density functionals used in practice are quite complicated and numerical quadrature must be used for their integration. There are difficulties inherent to such grid-based methods which do not arise in methods where all the requisite integrals are evaluated analytically, for example, as in Hartree-Fock theory. Unless great care is taken in the handling of the molecular grid, undesirable effects manifest themselves in the calculation. These various difficulties can be rigorously handled, but their improper treatment is a source of problems in most implementations. The goal of the Phase I feasibility study is to develop an analytically integrable density functional which yields a theoretical model chemistry similar to that of the Dirac functional. We will implement the resulting functional within the firm s quantum chemistry computer program. A practical analytic method would eliminate the spurious effects described above and at the same time would be quite likely to improve the computation time for small and medium-sized systems. The commercial benefits are apparent by measuring the substantial increase in both the quality of the results and the efficiency of the system resulting in increased research productivity and cost effectiveness.