b'Multi-scale ThermalFirst principles modeling of thermal properties in solids allows researchers to Properties Prediction innarrow the field of possible materials and geometries for new thermoelectric devices, quantum computing components, and nanosensors, enabling the Multiphysics Object- substantial time and monetary savings.Oriented SimulationT he physics of thermal properties in solids are inherently multi-scale, arising Environment via a Generalfrom atomistic processes and interactions with the microstructure of a material, such as grain boundaries and point defects. Heat transport in Boltzmann Solver solids via conduction occurs through the transport and scattering of electrons and phonons. The a priori forecasting of fundamental quantities, such as temperature distribution, heat flux, and thermal conductivity typically employs the Boltzmann transport equation to predict the macroscopic behavior of a materials system in terms of the microscopic dynamics of its heat carriers.TOTAL APPROVED AMOUNT:This project established a new MOOSE module, Boltzmann, dedicated to phonon $125,000 over 1 year and thermal electron transport. This is a deterministic transport method using the continuous FEM to resolve the geometric domain and discrete ordinates to resolve the PROJECT NUMBER:angular domain. Thermal electron transport is coupled through a spatially averaged 20A1049-012 temperature in the Fermi-Dirac statistics, which describe the thermodynamic PRINCIPAL INVESTIGATOR:equilibrium distribution of electrons. The transport algorithm leverages these statistics Jackson Harter as the Boltzmann transport equation to calculate the deviation from equilibrium, which leads to the description of a temperature field, heat flux, and electronic/CO-INVESTIGATORS: thermal conductivity. This method was tested on two-dimensional films of silicon at Andrea Jokisaari, INL room temperature based on the available material properties, but the method works Sebastian Schunert, INL the same for metallic materials. In addition, spectrally resolved phonon transport is Shuxiang Zhou, INL implemented with the same spatial and angular discretization as thermal electron transport. A new algorithm and method also were developed that leverage the equilibrium Bose-Einstein statistics for non-interaction particles.Boltzmann provides a platform to sustain increasingly sophisticated models of the collision physics inherent to the transport of the heat carriers. This software simulates thermal electron and phonon transport to predict fundamental thermal quantities based on ab initio material property data, which may be used at the engineering scale. This powerful capability provides a critical bridge across the length scales, allowing the prediction of material properties based on ab initio approaches. The simulation of coupled electron-phonon transport allows for a holistic depiction of the detailed, mechanistic process occurring at the atomistic- and nano-scales.PUBLICATION:Harter, J. R., T. S. Palmer, and P. A. Greaney, Predicting mesoscale spectral thermal conductivity using advanced deterministic phonon transport techniques, Chapter Heat flow around a cluster of xenon bubbles5 in Advances in Heat Transfer, Abraham, J. P., J. M Gorman, and W. J. Minkowycz in a uranium dioxide lattice. (eds.), vol. 52 (2020).41'