PI: Xiulin Ruan, Purdue University Proposal Number: CBET-1150948
The proposed effort will enable the prediction of thermal conductive and radiative properties of solids from first principles. Thermal conductivity and far-infrared thermal radiative properties of solids are critical issues in many modern and emerging applications such as thermal management, electronics, photovoltaics, and thermoelectrics. Both properties, although seemingly unrelated, are governed in the atomic scale by the dispersion relation and relaxation time of the same thermal energy carrier called phonon. To guide the design and synthesis of these materials, it is highly desirable to predict their thermal properties from first principles, i.e., from their atomic structures without the use of adjustable parameters. However, existing classical interatomic potentials are inaccurate even for standard materials such as silicon and carbon since the potentials were not intended for the purpose of thermal transport modeling. For most other solids, the classical potentials haven't been developed yet, making the prediction of their thermal transport properties impossible. Therefore, it is the objective of this proposal to formulate new methodologies that can develop accurate interatomic potentials or can completely bypass the use of classical potentials, for thermal property prediction. Toward this goal, two multiscale multiphysics methods will be developed in parallel. In the first method, first principles calculations will be used to develop accurate classical interatomic potentials that are intentionally optimized for thermal transport modeling, and the potentials will then be employed in classical MD to predict thermal conductivity. In order to bypass the challenging and tedious potential development process, the second method will introduce a new tight-binding molecular dynamics (TBMD) method to produce the trajectory of atoms, which will then be used in phonon spectral analysis to obtain spectral phonon relaxation time as well as thermal conductivity and radiative properties. The predictive power will be demonstrated first on standard materials such as silicon, and then on a range of important but complex thermoelectric and photovoltaic materials, including Bi2Te3 and GaAs bulk and nanomaterials.
The intellectual merit of the proposal centers around fundamentally new prediction methods based on first principles for both thermal conductive and radiative properties. The tight binding MD together with phonon spectral analysis will revolutionize thermal transport property prediction of a wide range of materials of technological importance, on which atomic scale prediction was not possible before due to the lack of empirical interatomic potentials. The methods will also be used on practically important thermoelectric and photovoltaic nanomaterials, including Bi2Te3 and GaAs, for the first time to guide experimental synthesis.
The research effort will impact thermal science and education/outreach programs. The new prediction methods will be of broad interest due to their generality. Important applications, including thermal management, thermoelectrics, electronics, and photovoltaics will benefit from the new insights generated using these methods. Under-represented and undergraduate students will continue to be involved in research. A key education/outreach component would be the dissemination of the research and education codes resulted from this project to nanoHUB and thermalHUB for general public use. Comprehensive documentation, online lectures, and tutorials explaining the codes will be provided. These materials will be of wide interest in the PI's field given the new capabilities they provide.
