Atomistic Design of Thermal and Electrical Transport in Materials with Dislocations: From High Power Electronics to Thermoelectrics

• Applicant: Professor Dr. Thomas Frauenheim
• Subject Area: Theoretical Condensed Matter Physics ; Synthesis and Properties of Functional Materials
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429844621

Recent advances in material synthesis controlled by dislocations suggest the novel possibility of engineering dislocations in nanomaterials. To leverage these advances and guide the synthesis of materials with engineered dislocations, accurate models for the dislocation-transport property relationship are needed. We propose research to advance the atomistic computational techniques and theoretical con-cepts needed to understand and predict the structure-transport properties across the material space. The extended strain fields and dynamic fluttering of the dislocations, and their impact on electronic properties are computationally tractable with the density functional theory based tight-binding (DFTB) method. To enable predictions in the thermal domain, we propose to couple DFTB with (i) a many-body non-equilibrium Green’s-function approach for quantum phononic transport with inter-atomic anharmonicity, (ii) an equilibrium objective molecular dynamics method for computing phonon band structure, lifetime, and group velocity calculations, and (iii) wave packet methods for studying phonon propagation and scattering. We will apply the developed tools to investigate ways to impart maximal or minimal lattice ther-mal conductivity while maintaining a large charge carrier mobility and Seebeck coefficient in bulk, one-dimensional, and two-dimensional materials. (i) Simulations of dislocations in bulk materials will target an understanding of the experimentally observed dramatic improvements in the thermoelectric figure of merit in materials with low intrinsic thermal conductivities and em-bedded dense dislocation arrays along grain boundaries. (ii) Nanowires are attractive nanostructures for achieving high thermoelectric performances, but the impact of dislocations located at their core is unknown. Simulations of nanowires storing dislocations aim to uncover a new important mechanism (phonon-dislocation scattering) for boosting the thermoelectric figure of merit. (iii) Two-dimensional materials are of tremendous importance for nanoelectronics devices, but the arrays of dislocations located at their grain boundaries (inherent extended defects) are prone to induce unwanted effects like severe self-heating. Investigations will un-cover dislocations array models that deliver optimal electrical charge transport with minimum heat generation at the grain boundaries.

• DFG Programme: Research Grants