Computational Chemistry of Clusters and Crystals

团簇和晶体的计算化学

• 批准号: 1361586
• 负责人: So Hirata
• 金额: $ 41.34万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1361586&HistoricalAwards=false
• 关键词: Computational; Chemistry; Clusters; Crystals

So Hirata of the University of Illinois at Urbana-Champaign is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division, the Condensed Matter and Materials Theory program in the Division of Material Research and the Computational and Data-enabled Science and Engineering Program (CDS&E) to develop computational approaches and software for the study of molecular crystals. Molecular crystals are a large, important class of solids that consist of well-defined molecular units bound by weak interactions. They include nature's most abundant and important solids such as the ices of the atmospheric species of Earth and other planets. Synthetic chemists can fashion molecules that aggregate into superstructures, which, if crystalline, are also molecular crystals. Some explosives and many drugs fall into this category. Some molecular crystals display optical and electronic properties making them suitable for optoelectronic devices such as solar cells. The goal of this project is to develop a general computational method for molecular crystals and related ionic crystals as well as organic molecular superconductors. The principal investigator and his coworkers develop software to predict the structure, optical and thermal properties, and phase behavior of organic crystalline solids with unprecedented accuracy and applications in high-pressure chemistry, geochemistry, planetary science, and materials science. This research activity involves innovative education in physical chemistry. A series of physical chemistry lectures is recorded and made available online with a matching set of problems, releasing all face-to-face classroom hours for problem solving, student's explanations of solutions, and discussions. The energy of a molecular crystal is approximated as a sum of the energies of its constituent fragments embedded in the self-consistently determined electrostatic environment of the crystal. The fragment energies are, in turn, evaluated by sophisticated molecular ab initio electronic structure methods. This allows an accurate calculation of a variety of properties of solids under finite temperature and pressure (structure, equation of state, infrared, Raman, inelastic neutron scattering spectra, heat capacity, enthalpy, Gibbs energy) at such high levels of fidelity as second- and higher-order perturbation theory or coupled-cluster theory. This project implements this method into robust and well-documented software that exploits the method's natural parallelism and makes it available for the broader scientific community. Furthermore, the project extends this method to energy bands and ionic crystals as well as organic molecular (super) conductors. The underlying idea that enables these calculations is the linear-combination-of-molecular-orbital (LCAO) crystal-orbital theory, a coarse-grained extension of the LCAO molecular-orbital concept, which has dominated computational quantum chemistry since its inception. By expanding the wave function of an organic molecular crystal, for instance, as a linear combination of its charge configurations, which, in turn, are treated by the aforementioned embedded-fragmentation scheme, this method describes charge transfer between constituent molecular units in these solids and thus charge density waves, spin density waves, and metallic as well as possibly superconducting states.

伊利诺伊大学厄巴纳-香槟分校的Hirata得到了化学学部化学理论、模型和计算方法项目、材料研究部凝聚态物质和材料理论项目以及计算和数据驱动科学与工程项目（CDS&amp；E）的奖励，以开发用于研究分子晶体的计算方法和软件。分子晶体是一类大型的、重要的固体，由定义明确的分子单元通过弱相互作用结合而成。它们包括自然界最丰富和最重要的固体，如地球和其他行星大气中的冰。合成化学家可以塑造聚集成上层结构的分子，这些上层结构如果是结晶的，也是分子晶体。一些爆炸物和许多毒品就属于这一类。一些分子晶体显示出光学和电子特性，使它们适合于光电子器件，如太阳能电池。本项目的目标是开发一种分子晶体和相关离子晶体以及有机分子超导体的通用计算方法。首席研究员和他的同事们开发了软件来预测结构、光学和热性质，以及有机结晶固体的相行为，其精度前所未有，并应用于高压化学、地球化学、行星科学和材料科学。这项研究活动涉及物理化学的创新教育。一系列物理化学讲座被记录下来，并与一套匹配的问题一起在网上提供，释放所有面对面的课堂时间来解决问题，学生对解决方案的解释和讨论。分子晶体的能量近似为嵌入在自一致确定的晶体静电环境中的其组成片段的能量之和。碎片的能量，反过来，由复杂的分子从头算电子结构方法评估。这允许在有限温度和压力下精确计算固体的各种性质（结构，状态方程，红外，拉曼，非弹性中子散射光谱，热容量，焓，吉布斯能量），其保真度与二阶和高阶微扰理论或耦合簇理论一样高。该项目将该方法实现为健壮且文档完备的软件，该软件利用了该方法的自然并行性，并使其可用于更广泛的科学社区。此外，该项目将这种方法扩展到能带和离子晶体以及有机分子（超导体）。实现这些计算的基本思想是分子轨道线性组合（LCAO）晶体轨道理论，这是LCAO分子轨道概念的粗粒度扩展，从一开始就主导着计算量子化学。例如，通过扩展有机分子晶体的波函数，将其作为电荷构型的线性组合，进而由上述嵌入破碎方案处理，该方法描述了这些固体中组成分子单元之间的电荷转移，从而描述了电荷密度波、自旋密度波、金属以及可能的超导状态。