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MM: Fachverband Metall- und Materialphysik

MM 34: Methods in Computational Materials Modelling (methodological aspects, numerics)

MM 34.2: Talk

Thursday, April 4, 2019, 10:30–10:45, H44

The temperature dependence of surface and grain boundary energies from first principles — •Daniel Scheiber, Maxim Popov, and Lorenz Romaner — Materials Center Leoben Forschung GmbH

Material properties generally depend on temperature. While for many bulk properties, the temperature dependence has been well investigated in experiment and theory, for grain boundary and surface energies the topic has remained largely unexplored. A large gap exists between experimental measurements at elevated temperatures and ab-initio simulations performed at 0K. The explanation for these deviations could also be rooted in the missing temperature treatment in the simulations.

In this study, we investigate the temperature dependence grain boundary energies in tungsten. Within the quasi-harmonic approximation we evaluate the phonons using ab-initio density functional theory for different grain boundaries. With that the Helmholtz free energies for grain boundaries are evaluated as a function of temperature. Our simulations show considerable reduction in interface energy with temperature for all investigated grain boundaries and surfaces. This change in interface energy may be directly related to changes in segregation energy, as it is known that segregation scales with grain boundary energy. Finally, we discuss the limitations of our approach and compare the results to available experimental data.