First-principles study of the lattice dynamics, thermodynamic properties and electron-phonon coupling of YB6

Ying Xu, Lijun Zhang, Tian Cui, Yan Li, Yu Xie, Wen Yu, Yanming Ma, and Guangtian Zou
Phys. Rev. B 76, 214103 – Published 6 December 2007

Abstract

The electronic, vibrational, and superconducting properties of YB6 with pressure have been extensively studied using the ab initio calculations. The Fermi surface calculation indicates a pressure-induced electronic topological transition under compression. The lattice dynamic study strongly suggests the existence of phase transition in YB6 under high pressure by evidence of a pressure-induced phonon softening behavior. Moreover, the calculated electron-phonon coupling (EPC) of YB6 with both the linear response theory and the rigid-muffin-tin approximation suggested that pairing electrons are mainly mediated by the Y low-lying phonon vibrations, and the hardening of Y low-lying phonon frequency with pressure is responsible for the decreased EPC. The current superconducting theory agrees well with the experimental suggestions [R. Lortz et al., Phys. Rev. B 73, 024512 (2006)], but in apparent contrasts to earlier theoretical calculations [G. Schell et al., Phys. Rev. B 25, 1589 (1982)]. Furthermore, the thermodynamic calculations within the quasiharmonic approximation give an accurate description of the pressure-temperature dependence of the linear thermal-expansion coefficient, bulk modulus, specific heat, and overall Grüneisen parameters to compare with the experimental measurement.

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  • Received 10 June 2007

DOI:https://doi.org/10.1103/PhysRevB.76.214103

©2007 American Physical Society

Authors & Affiliations

Ying Xu1, Lijun Zhang1, Tian Cui1, Yan Li1, Yu Xie1, Wen Yu2, Yanming Ma1,3,*, and Guangtian Zou1

  • 1National Lab of Superhard Materials, JiLin University, Changchun 130012, People’s Republic of China
  • 2Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China
  • 3Laboratory of Crystallography, Department of Materials, ETH Zurich, HCI G 515, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland

  • *Corresponding author; mym@jlu.edu.cn

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Vol. 76, Iss. 21 — 1 December 2007

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