ELEMENTS: Anharmonic formalism and codes to calculate thermal transport and phase change from first-principles calculations

今天，晶体材料的大多数性质都可以通过计算得到高度精确的计算。然而，由于物理理论的性质，这些性质目前是在绝对零度下计算的。该项目的目的是开发方法和计算机代码，将弹性和热力学性质的计算扩展到高达1000摄氏度或更高的温度，在那里热膨胀变得重要，结构相变可能发生。这项工作可能对航空航天和汽车工业产生重大影响，这些工业使发动机和零件在非常高的温度下工作。我们将开发的工具能够准确预测材料的稳定性和热物理性质，即使它们没有在实验室中合成。这些计算的结果也将包括在材料数据库中，并有助于我们对新功能材料的行为的理解。这些工具将在开源许可下免费提供给研究社区，以便让社区参与进一步的开发和合作。在该项目中，将对一名博士后研究员和一名研究生进行计算、数据处理和存储方法方面的培训。我们还将开发模块，在项目负责人组织的夏季项目中，向K-12学生讲授能源、转换、储存和可持续性。拟议项目的任务是为材料物理社区提供基于新一代量子力学方法和第一性原理计算输入的工具，以实现两个具有挑战性的领域的进展：(1)高温下的热力学、介电、机械和热输运性质，其中非调和效应变得很重要；(2)预测固体-固体相变作为温度的函数，特别是在声子与电子自由度耦合的多功能材料中。这种方法将是系统化的，并适用于能够定量预测上述性质的实际材料。这些代码将在非平凡材料上进行测试和验证，例如过渡金属氧化物（TMOs），因为这些材料具有丰富的相变数量和涌现的多铁性相。这些材料及其在能源和信息存储和处理方面的应用也有大量的相变实验和理论数据可供验证。总之，这些及时的工具将使材料科学家能够以前所未有的精度预测或了解任意温度下非调和、复杂和多功能材料的热物理性质。该项目由计算机和信息科学与工程理事会的高级网络基础设施办公室资助，数学和物理科学理事会的材料研究部也提供资金。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Most properties of crystalline materials can today be calculated with a high degree of accuracy via computation. Due to the nature of the physical theories, these properties are, however, currently calculated at absolute zero temperature. The purpose of this project is to develop methodologies and computer codes to extend the calculation of elastic and thermodynamic properties to temperatures as high as 1000C or more, where thermal expansion becomes important and structural phase transitions can occur. This work can have a great impact in the aerospace and car industries, which make engines and parts operating at very high temperatures. The tools we will develop enable accurate prediction of stability and thermophysical properties of materials, even if they have not been synthesized in the lab. The results of these calculations will also be included in materials databases and help in our understanding of the behavior of new functional materials. These tools will be freely available to the research community under an open source license so as to engage the community in further development and collaboration. During this project a postdoctoral researcher and a graduate student will be trained in computing, data processing and storage methods. We will also develop modules to teach K-12 students about energy, its conversion, storage and sustainability during summer projects organized by the project lead.The mission of the proposed project is to provide to the materials physics community tools based on a new generation of quantum mechanical methodologies and input from first-principles calculations, to enable advances in two challenging areas: (1) thermodynamic, dielectric, mechanical and thermal transport properties at high temperatures where anharmonic effects become important, and (2) prediction of solid-solid phase transitions as a function of temperature, particularly in multifunctional materials, in which phonons are coupled to electronic degrees of freedom. This approach will be systematic, and applies to real materials enabling quantitative prediction of the above properties. The codes will be tested and validated on non-trivial materials such as transition metal oxides (TMOs) due to those materials having a rich number of phase transitions and emergent multiferroic phases. These materials and their applications in energy and information storage and processing also have a large amount of experimental and theoretical data on their phase transitions available, for validation. In summary, these timely tools will enable materials scientists to predict or understand thermophysical properties of anharmonic, complex and multifunctional materials at arbitrary temperatures with unprecedented accuracy.This project is funded by the Office of Advanced Cyberinfrastructure in the Directorate for Computer and Information Science and Engineering, with the Division of Materials Research in the Directorate for Mathematical and Physical Sciences also contributing funds.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.