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.

因此，伊利诺伊大学伊利诺伊大学乌尔巴纳 - 奇姆扬（Urbana-Champaign）的hirata得到了化学理论，模型和计算方法计划的奖项，在化学部门，材料研究和计算和数据支持科学与工程计划（CDS＆e）的凝结物问题和材料理论计划（CDS＆e）中，以开发用于研究分子水晶研究的计算方法和软件。分子晶体是由弱相互作用结合的明确定义的分子单位组成的大型，重要的固体类别。它们包括大自然最丰富，最重要的固体，例如地球和其他行星大气物种的冰。合成化学家可以塑造将汇总成超结构的分子，如果结晶也是分子晶体。一些爆炸物和许多药物属于这一类。一些分子晶体显示出光学和电子特性，使其适用于光电设备，例如太阳能电池。该项目的目的是开发一种用于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。 首席研究者和他的同事开发了软件，以预测具有前所未有的精度和在高压化学，地球化学，行星科学和材料科学中的精度和应用的有机晶体固体的结构，光学和热性能。这项研究活动涉及物理化学方面的创新教育。记录并在线记录了一系列物理化学讲座，并在线提供了一系列匹配的问题，从而释放了所有面对面的课堂，以解决问题，学生对解决方案的解释和讨论。分子晶体的能量被近似为其成分片段的能量之和，该片段嵌入了晶体的自敏确定的静电环境中。片段能量又通过复杂的分子电子结构方法进行评估。这允许在有限温度和压力下（结构，红外，拉曼，无弹性中子散射光谱，热容量，焓，吉布斯能量）在有限温度和压力下进行准确计算固体的各种特性），例如第二和更高的扰动理论或更高水平的延误性。该项目将该方法实现在强大且有据可查的软件中，该软件利用了该方法的自然并行性，并使该方法可用于更广泛的科学界。此外，该项目将此方法扩展到能带和离子晶体以及有机分子（超级）导体。启用这些计算的基本思想是分子轨道（LCAO）晶体轨道理论的线性组合，这是LCAO分子 - 轨道概念的粗粒度扩展，自从其发表以来，它一直占据了计算量子化学的主导。通过扩展有机分子晶体的波功能，例如，作为其电荷构型的线性组合，这反过来又通过上述嵌入式覆盖碎片的方案来处理，该方法描述了这些固体中组成分子单位之间的电荷传递，从而描述了这些固体中的构成分子单位，从而介绍了电荷密度波，旋转密度的波动，且可能是及其可能的，以及可能的且可能是超过的。