Publicatie voor Fritz Körmann in Nature Computational Materials

Nieuws - 11 augustus 2017

Onlangs ontving Fritz Körmann, onderzoeker bij de afdeling Materials Science and Engineering, al een vidi voor zijn onderzoek: 'How to mix the perfect high entropy alloy cocktail?' Deze week publiceerden Fritz Körmann en Marcel Sluiter, samen met Yuji Ikeda van de Kyoto University in Japan en Blazej Grabowski van het Max-Planck-Institut für Eisenforschung in Duitsland hun onderzoek in Nature Computational Materials. Körmann houdt zich bezig met het relatief jonge onderzoeksgebied van high entropy alloys waarbij hij via computersimulaties nieuwe legering ontwerp principes ontwikkelt voor extreme materiaaleigenschappen.

Abstract publicatiePhonon broadening in high entropy alloys (alleen in het Engels beschikbaar):

Refractory high entropy alloys feature outstanding properties making them a promising materials class for next generation high-temperature applications. At high temperatures, materials properties are strongly affected by lattice vibrations (phonons). Phonons critically influence thermal stability, thermodynamic and elastic properties, as well as thermal conductivity. In contrast to perfect crystals and ordered alloys, the inherently present mass and force constant fluctuations in multi-component random alloys (high entropy alloys) can induce significant phonon scattering and broadening. Despite their importance, phonon scattering and broadening have so far only scarcely been investigated for high entropy alloys. We tackle this challenge from a theoretical perspective and employ ab initio calculations to systematically study the impact of force constant and mass fluctuations on the phonon spectral functions of twelve body-centered cubic random alloys, from binaries up to five-component high entropy alloys, addressing the key question of how chemical complexity impacts phonons. We find that it is crucial to include both mass and force constant fluctuations. If one or the other is neglected, qualitatively wrong results can be obtained such as artificial phonon band gaps. We analyze how the results obtained for the phonons translate into thermodynamically integrated quantities, specifically the vibrational entropy. Changes in the vibrational entropy with increasing the number of elements can be as large as changes in the configurational entropy and are thus important for phase stability considerations.