Collaborative Research: Ab Initio Computation of Phonon Thermal Transport in Crystalline and Disordered Materials

Boston College, Chestnut Hill MA

Investigators

Abstract

1066634 Broido The lattice thermal conductivity is a fundamental thermal transport parameter that determines the utility of materials for specific thermal management applications. Accurate theoretical modeling of the lattice thermal conductivity is essential to numerous fields including microelectronics cooling, thermoelectrics, and even planetary science. The goal of this collaborative research effort will be to implement a theoretical approach to calculate the lattice thermal conductivity of crystalline and alloyed materials from first principles. A central feature of this approach is that it has no adjustable parameters. The focus at the Boston College site will be in using an exact numerical solution of the phonon Boltzmann equation to calculate the lattice thermal conductivity. The materials to be studied in this project include lead chalcogenides, I-V-VI2 semiconductors, and nanoparticle-in-alloy-structures. For nanostructured systems, such as the nanoparticles in alloys, a Non-Equilibrium Green?s Function approach will be implemented. The critical inputs for the transport modeling will come from harmonic and, where necessary, anharmonic interatomic force constants, whose calculation will be the focus of the Cornell site. The first principles approach has already demonstrated excellent agreement with measured high thermal conductivities of group IV semiconductors. The materials to be studied in this project are unified by their exceptionally low thermal conductivities and therefore provide an excellent test of the robustness of the theory. The measured thermal properties of many of these materials are well characterized and will provide an useful check of our calculated adjustable parameter-free results. Good agreement with measured data would further validate the predictive capability of this state-of-the-art theory in studying and understanding thermal transport and the lattice thermal conductivity in a wide range of materials for many thermal management applications. Intellectual merit: Current theories of the lattice thermal conductivity of materials are typically based on either highly parameterized relaxation time approximations or on purely classical molecular dynamics calculations. The rigorous first principles theory proposed here has no adjustable parameters and incorporates fully the quantum mechanical phonon scattering processes. It therefore could provide currently unavailable predictive power to support ongoing and future experimental studies of thermal transport in materials, as well as contributing to the development of new highly efficient materials engineered for desired thermal management applications. Broader impacts: The project will provide training for one postdoctoral researcher and one doctoral graduate student. In addition, several undergraduates including those from underrepresented groups will participate through NSF REU programs at both Boston College and Cornell sites. The computational tools to be developed during this project will be incorporated into the publicly available computing library of the Cornell Nanoscale Science and Technology Facility (CNF). The activity will also benefit society by aiding in the development of new materials with desired thermal transport properties. This will facilitate technological breakthroughs that may lead to the next generation of thermoelectric materials, thermal barrier coating materials, and thermal interface materials.