Density Functional Theory of Electronic Structure

电子结构密度泛函理论

• 批准号: 1607868
• 负责人: John Perdew
• 金额: $ 44.02万
• 依托单位: Temple University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1607868&HistoricalAwards=false
• 关键词: Density; Functional; Theory; Electronic; Structure

NONTECHNICAL SUMMARYThe Division of Materials Research and the Chemistry Division contribute funds to this award that will lead to more accurate computer modeling of molecules, chemicals, and materials. To do this the PI will focus on the "glue" that binds one atom to another to form molecules and materials which has the technical name exchange-correlation energy. Making this energy smaller strengthens the "glue" because electrons avoid close approaches to other electrons which have the same electric charge. The density of electrons determines the exchange-correlation energy, but the exact formula is not known. Nevertheless, it is possible to use a computer to predict what molecules and materials can exist, and with what properties, by using an approximate formula. The PI has developed approximate formulas that lead to good predictions of the properties of many materials and molecules as compared with actual experiments. In this research the PI will develop even more accurate approximations for the "glue" that still lend themselves to efficient simulation of molecules, and materials on a computer. The PI's most recent approximate formula is called SCAN. As a feature, it shares all the attributes of the exact formula that are known from fundamental principles of quantum mechanics that are possible for an approximation like SCAN. Nevertheless, no formula of this type can be exact; approximations of this type introduce a spurious interaction of an electron with itself. A major goal of this project will be to develop a widely-useful correction to overcome this source of error for SCAN.The development of more accurate approximations for the "glue" that holds atoms together leads to better predictions for the properties of chemicals, molecules, and materials. These predictions can lead to the discovery of new materials with desired properties for a wide range of applications from building and construction, to sophisticated electronic devices, to biomaterials for medical applications, and more. This research enables better computer modeling of materials with potential impact on the Materials Genome Initiative. This award also helps support the PI's efforts to develop better ways to help educate more high-school physics teachers,and to involve undergraduate students in the research.TECHNICAL SUMMARY The Division of Materials Research and the Chemistry Division contribute funds to this award that supports research in Kohn-Sham density functional theory, the most widely-used method to calculate ground-state energies or energy differences, equilibrium nuclear positions, and electron densities in atoms, molecules, and solids. The theory is exact in principle, although in practice the density functional for the exchange-correlation energy must be approximated. In the preceding award period, the Perdew research group developed SCAN, a "strongly constrained and appropriately normed" functional that is more accurate for diversely-bonded systems than comparably-efficient approximations. Satisfying all 17 known exact constraints that a semilocal functional can, the SCAN meta-generalized gradient approximation could replace the widely-used Perdew-Burke-Ernzerhof generalized gradient approximation.In the current award period, extensive tests will be made for SCAN and for SCAN with a long-range van der Waals correction. These tests would include the formation energies which determine relative stabilities of molecules and solids from the elements in their standard states, large reference-data sets for sp-bonded and transition-element-containing molecules, the polyacetylene chain, the ground-state crystal structures of solids that have proven challenging to get correct for , fundamental band gaps of solids, surface energies and work functions of metals, and adsorption energies for molecules on surfaces, A refined self-interaction correction to SCAN would seek to preserve the excellent SCAN description of equilibrium bonds for weakly-correlated systems while improving the description of stretched bonds, charge transfers, and strongly-correlated systems. A SCAN-like additive correction to the fully-nonlocal random phase approximation would be developed. Proof would be sought for a hypothesized tight lower bound on the exchange energy of any spin-unpolarized density. Finally, exchange-correlation energy differences for selected systems would be analyzed in a way that could lead to a better understanding of electronic systems and their properties, and of the successes of SCAN. The development of more accurate approximations for exchange-correlation functions will result in better predictions for the properties of atoms, molecules, and materials and can lead to the discovery of new materials with desired properties for a wide range of applications from building and construction to sophisticated electronic devices to biomaterials for medical applications and more. This research enables better computer modeling of materials with potential impact on the Materials Genome Initiative. This award also helps support the PI's efforts to develop better ways to help educate more high-school physics teachers, and to involve undergraduate students in the research.

非技术总结材料研究部和化学部为该奖项提供资金，这将导致对分子、化学品和材料进行更准确的计算机建模。为了做到这一点，PI将把重点放在将一个原子与另一个原子结合起来形成分子和材料的“胶”上，这种分子和材料的技术名称是交换-关联能。使这一能量变得更小会加强这种“粘合”，因为电子避免了与具有相同电荷的其他电子的接近。电子密度决定了交换相关能，但确切的公式尚不清楚。然而，通过使用近似公式，使用计算机来预测哪些分子和材料可以存在，以及具有哪些性质是可能的。PI已经开发出近似公式，与实际实验相比，这些公式可以很好地预测许多材料和分子的性质。在这项研究中，PI将开发出更精确的“胶”近似，这种“胶”仍然有助于在计算机上高效地模拟分子和材料。圆周率的最新近似公式称为扫描。作为一个特征，它共享从量子力学基本原理中已知的精确公式的所有属性，这些属性对于像扫描这样的近似是可能的。然而，这种类型的公式不可能是精确的；这种类型的近似引入了电子与其自身的虚假相互作用。该项目的一个主要目标是开发一种广泛适用的校正方法，以克服扫描扫描的这一误差来源。对将原子结合在一起的“胶”进行更准确的近似，可以更好地预测化学品、分子和材料的性质。这些预测可能导致发现具有所需性能的新材料，用于从建筑和建筑到复杂的电子设备，再到用于医疗应用的生物材料等广泛应用。这项研究使对可能对材料基因组倡议产生影响的材料进行更好的计算机建模成为可能。该奖项还有助于支持PI开发更好的方法来帮助培养更多的高中物理教师，并让本科生参与研究。技术摘要材料研究部和化学部向该奖项提供资金，支持Kohn-Sham密度泛函理论的研究，Kohn-Sham密度泛函理论是计算基态能量或能量差、平衡核位置和原子、分子和固体中电子密度的最广泛使用的方法。该理论在理论上是精确的，尽管实际上交换相关能的密度泛函必须是近似的。在之前的获奖期间，Perdew研究小组开发了SCAN，这是一种“强烈约束和适当规范”的泛函，对于不同键合的系统比相对有效的近似更准确。在满足半局部泛函所能满足的所有17个已知精确约束的情况下，SCAN准广义梯度近似可以取代广泛使用的Perdew-Burke-Ernzerhof广义梯度近似。在当前的获奖期内，将对SCAN和远程van der Waals校正的SCAN进行广泛的测试。这些测试将包括从元素在其标准状态下确定分子和固体的相对稳定性的形成能，sp键和含过渡元素的分子的大型参考数据集，聚乙炔链，已被证明具有挑战性的固体的基态晶体结构，固体的基本带隙，金属的表面能和功函数，以及表面分子的吸附能，对扫描的改进自作用校正将寻求保持对弱关联系统平衡键的出色扫描描述，同时改进对伸展键、电荷转移和强关联系统的描述。将发展一种对完全非局部随机相位近似的类似扫描的附加校正。任何自旋非极化密度的交换能都有一个假设的紧下限，这是可以找到的证据。最后，将对选定系统的交换相关能量差异进行分析，以便更好地了解电子系统及其性质，以及扫描的成功。交换相关函数的更精确近似的发展将导致更好地预测原子、分子和材料的性质，并可能导致发现具有所需性质的新材料，用于从建筑和建筑到复杂的电子设备到医疗应用的生物材料等广泛的应用。这项研究使对可能对材料基因组倡议产生影响的材料进行更好的计算机建模成为可能。该奖项还有助于支持PI开发更好的方法来帮助培养更多的高中物理教师，并让本科生参与研究。