Premelting hcp to bcc Transition in Beryllium

Y. Lu, T. Sun, Ping Zhang, P. Zhang, D.-B. Zhang, and R. M. Wentzcovitch

Phys. Rev. Lett. 118, 145702 – Published 7 April 2017

Abstract

Beryllium (Be) is an important material with wide applications ranging from aerospace components to x-ray equipment. Yet a precise understanding of its phase diagram remains elusive. We have investigated the phase stability of Be using a recently developed hybrid free energy computation method that accounts for anharmonic effects by invoking phonon quasiparticles. We find that the $hcp \to bcc$ transition occurs near the melting curve at $0 < P < 11 GPa$ with a positive Clapeyron slope of $41 \pm 4 K / GPa$ , which is more consistent with recent experimental measurements. This work also demonstrates the validity of this theoretical framework based on the phonon quasiparticle to study the structural stability and phase transitions in strongly anharmonic materials.

Received 30 November 2016

DOI:https://doi.org/10.1103/PhysRevLett.118.145702

Physics Subject Headings (PhySH)

Anharmonic lattice dynamics Phase diagrams Solid-solid transformations

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Y. Lu¹, T. Sun², Ping Zhang³, P. Zhang^4,1, D.-B. Zhang^1,*, and R. M. Wentzcovitch⁵

¹Beijing Computational Science Research Center, Beijing 100193, China
²Key Laboratory of Computational Geodynamics, University of Chinese Academy of Sciences, Beijing 100049, China
³Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
⁴Department of Physics, University at Buffalo, State University of New York, Buffalo, New York 14260, USA
⁵Materials Science and Engineering, Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA and Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York 10964, USA