Novel first-principles methods for studying thermoelastic properties of materials

非技术总结该奖项支持旨在开发新方法来计算材料热弹性参数的计算研究活动，例如热膨胀系数，以及不同温度和压力下的线性和非线性弹性常数。当受到温度和/或压力的变化时，材料膨胀或收缩。在加热或由外部机械力引起的材料体积的变化具有原子起源，因为它们来自原子的量子运动，它们的空间排列以及形成材料的原子之间的化学键的性质。计算与体积变化相关的材料系数作为温度和压力的函数具有基础和技术重要性。例如，计算材料的热膨胀系数对于设计在可变温度下运行的可靠技术设备至关重要，预测矿物在温度和压力的延长间隔内的弹性常数值对于解释地震数据至关重要。在这个项目中，PI将开发新的，通用的，计算效率高的方法来计算热弹性参数，通过使用精确的和无参数的原子描述的材料。PI将应用新方法研究地质相关矿物和结构应用金属合金的热弹性特性。该奖项还支持研究生和本科生的培训和教育。PI将为本科生开发基于模拟的物理化学课程。将采取创新策略，吸引少数民族学生参加课程，并在PI的实验室进行本科研究。此外，PI将为高中生提供为期两周的暑期课程，旨在展示计算机模拟作为学习，探索和做科学的手段。技术总结该奖项支持旨在开发和应用方法来计算材料的热弹性参数的计算研究活动。热膨胀系数和弹性常数是重要的材料参数。这些热弹性参数的常规计算的新的和有效的第一原理方法是必要的，以弥补实验数据的缺乏，在实验上无法达到的极端条件下研究材料的热弹性行为，并使高通量筛选有用的机械参数在相关的环境条件下，如金属合金的结构应用的理想强度。在这个项目中，PI将开发新的，通用的，计算效率高的方法依赖于准谐波近似。这些方法将允许计算热膨胀系数，以及在有限温度和恒定体积下材料的二阶和最显著的三阶弹性常数。此外，由于使用数值外推技术，新的方法将允许获得，在几乎没有额外的计算成本，一个完整的热弹性表征的材料在附近的任意参考状态。在该项目中，这些方法将用于预测与地质相关的低对称性矿物在高压和高温下的状态方程和弹性常数，并研究选定的高熵金属合金在有限温度下的热膨胀特性和理想强度。该奖项还支持研究生和本科生的培训和教育。PI将为本科生开发基于模拟的物理化学课程。将采取创新策略，吸引少数民族学生参加课程，并在PI的实验室进行本科研究。此外，PI还将为高中生提供为期两周的暑期项目，旨在展示计算机模拟作为学习、探索和从事科学的一种手段。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports computational research activities aimed at developing novel methods to calculate thermoelastic parameters of materials, such as the coefficient of thermal expansion, and linear and non-linear elastic constants at different temperatures and pressures. Materials expand or contract when subjected to changes of temperature and/or pressure. The changes in the material's volume upon heating or induced by external mechanical forces have an atomistic origin, as they emerge from the quantum motion of atoms, their spatial arrangement, and the nature of the chemical bonds between the atoms forming the material. Calculating the material coefficients related to changes in volume as a function of temperature and pressure is of both fundamental and technological importance. For example, calculating the coefficient of thermal expansion of materials is crucial for designing reliable technological devices operating at variable temperatures, and predicting the values of elastic constants of minerals over extended intervals of temperature and pressure is essential to interpret seismic data. In this project, the PI will develop novel, general, and computationally efficient methods to calculate thermoelastic parameters by using accurate and parameter-free atomistic descriptions of a material. The PI will apply the new methods to study the thermoelastic properties of minerals of geological relevance and metal alloys for structural applications. This award also supports the training and education of graduate and undergraduate students. The PI will develop a simulation-based physical-chemistry course for undergraduate students. Innovative strategies will be adopted to attract minority students to attend the course and conduct undergraduate research in the PI's lab. In addition, the PI will offer two-week long summer programs for high school students aimed at showcasing computer simulations as means to learn, explore, and do science.TECHNICAL SUMMARYThis award supports computational research activities aimed at developing and applying methods to calculate thermoelastic parameters of materials from first principles. Coefficients of thermal expansion and elastic constants are important materials parameters. Novel and efficient first-principles methods for routine calculations of these thermoelastic parameters are needed to compensate the lack of experimental data, to study thermoelastic behaviors of materials under extreme conditions that are unattainable experimentally, and to enable the high-throughput screening of useful mechanical parameters at relevant environmental conditions, such as the ideal strength of metal alloys for structural applications. In this project, the PI will develop novel, general, and computationally efficient methods relying on the quasi-harmonic approximation. These methods will allow calculation of the coefficient of thermal expansion, and both second- and, most notably, third-order elastic constants of a material at finite temperature and constant volume. Furthermore, thanks to the use of numerical extrapolation techniques, the novel methods will allow the obtainment, at virtually no extra computational cost, a full thermoelastic characterization of a material in the neighborhood of an arbitrary reference state. In this project, these methods will be used to predict the equation of state and elastic constants at high pressures and temperatures of low-symmetry minerals of geological relevance, and to study the thermal expansion properties and ideal strength at finite temperature of selected high-entropy metallic alloys.This award also supports the training and education of graduate and undergraduate students. The PI will develop a simulation-based physical-chemistry course for undergraduate students. Innovative strategies will be adopted to attract minority students to attend the course and conduct undergraduate research in the PI's lab. In addition, the PI will offer two-week long summer programs for high school students aimed at showcasing computer simulations as a means to learn, explore, and do science.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.