Berlin 2018 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 69: Structural Materials (Steels, light-weight materials, high-temperature materials)
MM 69.5: Talk
Friday, March 16, 2018, 10:30–10:45, H 0106
Influences of temperature and configurational disorder on electronic properties of boron carbide — •Annop Ektarawong1, Sergei Simak1, and Björn Alling1,2 — 1Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden — 2Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany
Long-standing controversial issues, concerning the electronic properties of boron carbide, are emphasized by large discrepancies between experiments and theoretical calculations. One of these is the overestimation of the bandgap of B4C by standard DFT functionals, known to underestimate the bandgaps of all other materials. Another is the predicted metallic state of B6.5C in conflict with its experimental semiconducting state. With the aim of resolving such discrepancies, we investigate from first principles influences of temperature and configurational disorder, induced by low-energy defects, on electronic properties of the material. Regardless of the temperature, our results reveal a large variation in size of the bandgap and the appearance of the mid-gap states, both depending on the material’s atomic configuration and composition, and also yield a fairly good agreement, compared to the experiments. The ab initio molecular dynamics simulations reveal the volumetric thermal expansion due to the lattice vibrations has a minimal impact on the bandgap of the material, while a major decrease of the bandgap is caused by explicit atomic displacements, induced by the vibrations. The temperature-dependent bandgaps of boron carbides, especially, B4C and B4.3C, will also be presented and discussed.