Computational Methods for Electronic Structure

电子结构的计算方法

• 批准号: 0404853
• 负责人: David Ceperley
• 金额: $ 54万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-11-01 至 2008-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0404853&HistoricalAwards=false
• 关键词: Computational; Methods; Electronic; Structure

The long-range goal of this research is to develop theoretical and computational methods to predict accuratelythe properties of many-electron systems and then to apply the methods to important condensed mattersystems. The focus of this research is primarily on the development and application of quantumMonte Carlo (QMC) methods. However, part of the research attempts to tie these approaches to othertheoretical issues such as the fundamental distinction between metals and insulators in terms of the manybodyelectron wave function.QMC can provide very accurate results for electronic systems: the most well-known example is the homogenous electron gas where QMC has provided the benchmark upon which are based most density functional (DFT) calculations. DFT-based methods are the only current method feasible for accurate large-scale simulations of realistic systems; however, even the improved functionals have well-known defects. The past few years have seen substantial progress in coupling the simulation of ions at a finite temperature with QMC simulation of the electrons (the CEIMC method). In addition to being more accurate, in cases where other averaging must be performed, the QMC approach can be as efficient as DFT-based approaches. Applications to extended systems of hydrogen are now in production. In the near futurethere will be development of QMC methods, with emphasis upon more accurate wave functions, improvedboundary conditions, and new methods able to use much larger computational facilities efficiently.The research will enable applications to elements with core electrons using more accurate pseudopotentials.Methods to calculate electronic forces will enable dynamical calculations of ionic systems.Applications of the methods will include hydrogen throughout the whole phase diagram of temperatureand pressure. Although there have been numerous previous QMC and DFT simulations, the CEIMCmethod removes most of their limitations. The connection between the insulator-metallic transition, theatomic molecular-transition and temperature and zero point effects is still lacking in current approaches.The simulations should clarify the situation, especially under conditions where experiment is non-existentor unreliable. A further challenge is the microscopic simulation of water from first principles, which isabsolutely fundamental to many scientific questions and which appears to be within reach of QMC simulation.The power of this approach can be applied to other problems, for example, new methods to simulateelectrons and their spin states in real nanostructure devices, potentially more accurately and efficientlythan with existing grid-based approaches. The entire device can be simulated by coupling tworandom walks-one to solve the electrostatic equations in a complicated structure and another for the Nbodyquantum equation for the electrons.The computational complexity of the simulation of the basic equations of matter (onclassical not quantum computers) is a very important and fundamental issue. The challenge is to solveaccurately problems with many interacting particles, including strongly interacting systems and cooperativephenomena. QMC methods have made it possible to compute the thermodynamic properties of bosonicsystems, including superfuidity. However, the fermion sign problem is a critical issue limitingpresent work, and steps toward solving or minimizing the sign problem are among the outstanding challengesin computational science. In addition, development of new computational approaches frequentlyleads to new theoretical understanding as well as algorithms useful in other disciplines.The development of these computational quantum methods will have a qualitative impactupon the course of many fields of science including physics, materials science, chemistry and evenbiology, by enabling much more accurate, and potentially faster, simulation of a broad range of systems.The calculations will resolve questions about the properties of hydrogen at high temperatures and pressures,the basis of models for the formation of Jovian planets; the microscopic properties of water andsolutions; and properties of nanoscale systems. The research is carried out primarily by graduate studentsand postdocs who often go later to industry, thus transferring the latest computational methods. Algorithmsand software developed as a result of the research will be made available to the general researchcommunity through the Materials Computation Center and used in undergraduate courses, graduatecourses, and summer schools at the University of Illinois and elsewhere.

这项研究的远距离目标是开发理论和计算方法，以准确预测许多电子系统的特性，然后将方法应用于重要的凝结物质系统。这项研究的重点主要在于Quantummonte Carlo（QMC）方法的开发和应用。然而，部分研究试图将这些方法与其他理论问题联系起来，例如在许多Bodyelectron Wave函数方面，金属和绝缘体之间的基本区别。QMC可以为电子系统提供非常准确的结果：最著名的示例是同质电子气体在其中QMC基于哪些基于基于哪些基于的基于基于最大密度（DFT）功能的基准。基于DFT的方法是对现实系统进行准确的大规模模拟的唯一当前方法。但是，即使改进的功能也具有众所周知的缺陷。在过去的几年中，在有限温度与电子模拟的QMC仿真耦合离子的模拟方面取得了长足进展（CEIMC方法）。除了更准确的情况下，如果必须执行其他平均值，QMC方法还可以与基于DFT的方法一样有效。现在生产到扩展氢系统的应用。在近乎未来的情况下，将开发QMC方法，强调更准确的波浪函数，改善的条件以及能够有效地使用更大的计算设施的新方法。该研究将使使用更准确的PSEUDOPOTICATS的元素对核心电子的元素进行应用，以计算整个相位的系统范围。温度压力。尽管以前有许多QMC和DFT模拟，但CEIMCMETHOD消除了其大部分局限性。在当前方法中，仍然缺乏绝缘子金属物质过渡，胰蛋白分子过渡和温度以及零点效应之间的联系。模拟应阐明情况，尤其是在实验不可靠的条件下。另一个挑战是从第一原理中对水的微观模拟，这绝对是许多科学问题的基础，并且似乎在QMC模拟的范围内。可以通过耦合tworandom步行来模拟整个设备，以在复杂的结构中求解静电方程，而另一个用于电子方程的静电方程。电子的计算复杂性（基本方程式（On Classical Insclassicic of Classical Inscon）的计算复杂性）是一个非常重要的，非常重要的和基本问题。面临的挑战是要与许多相互作用的粒子（包括强烈相互作用的系统和合作型苯酚）进行溶解问题。 QMC方法已使计算包括超级成果在内的玻色子系统的热力学特性成为可能。但是，费米昂的标志问题是一个关键问题限制了列表工作，而解决或最小化标志问题的步骤是在计算科学中的挑战之一。此外，开发新的计算方法经常为新的理论理解以及在其他学科中有用的算法方面，这些计算量子方法的发展将产生定性的影响，即许多科学领域的过程，包括物理，材料科学，化学和偶数学，通过使得越来越准确的范围构成范围的范围，该系统范围更广泛地构成了范围，该系统的范围很广，该系统的范围越来越高，并构成了范围的范围。温度和压力，是乔维安行星形成的模型的基础；水和溶液的微观特性；和纳米级系统的特性。这项研究主要是由研究生和博士后进行的，他们经常以后进入行业，从而转移了最新的计算方法。由于研究的算法和软件将通过材料计算中心提供给一般研究社区，并用于伊利诺伊大学和其他地方的本科课程，毕业生和暑期学校。