Novel first-principles methods for studying thermoelastic properties of materials

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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.