Regensburg 2013 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 18: Computational Materials Modelling - Phase Stability I

MM 18.1: Vortrag

Dienstag, 12. März 2013, 10:15–10:30, H24

Stability and superconductivity of Ca-B under pressure — •Sheena Shah¹ and Aleksey Kolmogorov² — ¹University of Oxford, UK — ²Binghamton University - SUNY, USA

In the search for MgB₂-like phonon-mediated superconductors, we have carried out a systematic DFT-based evolutionary crystal structure search of the whole Ca_xB_1−x system at gigapascal pressures. A set of diverse ground state boron structures are identified for CaB, CaB₂, CaB₄ and CaB₆. The monoboride is predicted to be superconducting at 5 K. Others are predicted to be superconducting at lower temperatures, demonstrating the inverse correlation between thermodynamic stability and superconducting properties. Finally, structural rules have been established for the thermodynamic stability of these alkaline earth metal borides with pressure. For example, we show that ThB₄-type CaB₄ is stable at ambient pressure since the ionic radius of Ca²⁺ is an ideal fit for the boron network.