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NANO2021-Nanoteknologi og nye materiale

Phonon lifetimes; unifying inelastic neutron scattering measurements with first-principle calculations

Alternative title: Fononlevetider: en kombinasjon av uelastisk nøytronspredning og beregninger

Awarded: NOK 11.9 mill.

Our environmental impact is massive; thus, we urgently need to reshape our energy consumption. One key point resides in thermal management solutions, such as waste heat recovery and conversion, and localized and integrated thermoregulation which increases comfort, lifespan and reduces energy waste. Solid-state materials can and are used in thermal management, without the need for moving parts, such as high entropy alloys and thermoelectric materials. Thermoelectric materials can be used as energy converters, they can harvest waste heat and convert energy to electricity, or be used as spot-sized solid-state refrigerators. Microscopically, these applications are linked to the characteristics of atomic vibrations, which ultimately define the thermal properties. To optimize existing or discover new materials, it is important to fully understand how atomic vibrations interact and how those interactions affect their lifetime. If you think about these vibrations as waves, the lifetime is related to how far that wave can propagate through the material before dissipating. In this project, scientists at the University of Stavanger, SINTEF, Technical University of Denmark, the Helmholtz-Zentrum Berlin and collaborators will work together to develop new experimental and computational methodologies based on high-resolution neutron techniques to gain accurate insights into the lifetime of these atomic vibrations. We will compute, measure, and analyze the vibrations’ lifetimes and thermal conductivities of key materials. The resultant methodologies will allow us to predict macroscopic thermal properties from more accessible microscopic properties, like atomic positions. We will bring screening calculations closer to reality, facilitating the discovery of materials for innovative thermal management solutions and gain deeper fundamental knowledge of how the atomic vibrations interact in materials.

We propose to develop a coherent strategy to compute, measure and analyse phonon lifetimes and thermal conductivities for advanced materials, which will make possible to predict new materials for thermal management and yield the possibility to predict new or better optimized thermoelectric materials containing non-toxic and earth-abundant elements. This coherent strategy is based on computational developments, implementing both anharmonic and incoherent effects, in addition to the temperature effects on the phonon and electrical properties. These will be based on density functional theory (DFT) and post-DFT methods like screened Green’s functions (GW) and time-dependent-DFT (TDFT) and developments therein. In combination, this will allow us to develop generic workflows for each computational task and execute a large-scale screening study after initial experimental verification using three selected thermoelectric materials, strontium titanate, a skutterudite compound and a clathrate compound. We will determine the phonon lifetimes in the selected benchmark systems with high precision. A novel combination of the highest energy and momentum resolution neutron scattering techniques and Raman scattering will be used. Instrumental resolution functions will be revised and resolution functions for the future spectrometer BIFROST at the European Spallation Source will be computed. The scope of this proposal demands a highly experienced project group with top international research partners from different fields, such as neutron instrumentation and atomic-scale modelling. The project will mainly be executed by two national partners: University of Stavanger (UiS) and SINTEF and two international partners: Helmholtz-Zentrum Berlin and the Technical University of Denmark, thus ensuring knowledge transfer and contributing to the development of national expertise within these techniques.

Funding scheme:

NANO2021-Nanoteknologi og nye materiale