Regensburg 2019 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 31: Nitrides: Preparation and characterization II
HL 31.4: Vortrag
Mittwoch, 3. April 2019, 15:45–16:00, H31
A quantum-mechanical study of pressure-induced iso-structural transition in YN and ScN characterized by a reversal in their elastic anisotropy — •Martin Friák1,2, Pavel Kroupa1,3, David Holec4, and Mojmír Šob5,1,2 — 1Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno, Czech Republic — 2Central European Institute of Technology, CEITEC MU, Masaryk University, Brno, Czech Republic — 3Department of Physics, Imperial College London, London, United Kingdom — 4Department of Materials Science, Montanuniversität Leoben, Leoben, Austria — 5Department of Chemistry, Faculty of Science, Masaryk University, Brno, Czech Republic
Using quantum-mechanical calculations of 2nd- and 3rd-order elastic constants for YN and ScN with the rock-salt (B1) structure we predict that the studied materials change the fundamental type of their elastic anisotropy by rather moderate hydrostatic pressures of a few GPa. In particular, YN with its zero-pressure elastic anisotropy characterized by the Zener anisotropy ratio AZ = 2C44/(C11 - C12) = 1.046 becomes elastically isotropic at the hydrostatic pressure of 1.2 GPa. The lowest values of the Young’s modulus (so-called soft directions) change from ⟨100⟩ (in the zero-pressure state) to the ⟨111⟩ directions (for pressures above 1.2 GPa). It means that the crystallographic orientations of stiffest (also called hard) elastic response and that of the softest one become reversed. Qualitatively the same type of transition is predicted for ScN with the zero-pressure value of the Zener anisotropy factor AZ = 1.117 and the transition pressure about 6.5 GPa.