Eur. Phys. J. B (2018) 91: 128
https://doi.org/10.1140/epjb/e2018-90166-9

Regular Article

Gradient-level and nonlocal density functional descriptions of Cu-Au intermetallic compounds^★

¹ Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology, Stockholm 100 44, Sweden
² Department of Physics and Astronomy, University of Turku, 20014 Turku, Finland
³ Turku University Centre for Materials and Surfaces (MatSurf), Turku, Finland
⁴ Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest, Hungary
⁵ Department of Physics and Astronomy, Division of Materials Theory, Uppsala University, Box 516, 75121 Uppsala, Sweden

^a e-mail: hpleva@utu.fi

Received: 13 March 2018
Received in final form: 25 April 2018
Published online: 22 June 2018

Abstract

We use three gradient level and two nonlocal density functional approximations to study the thermodynamic properties of Cu-Au compounds. It is found that a well-designed gradient level approximation (quasi non-uniform approximation, QNA) reproduces the experimental equilibrium volumes and the formation energies of L12 and L10 phases. On the other hand, QNA predicts a non-existent β₂ phase, which can be remedied only when employing the nonlocal hybrid-level Heyd-Scuseria-Ernzerhof (HSE06) or Perdew-Burke-Ernzerhof (PBE0) approximations. Gradient-level approximations lead to similar electronic structures for the Cu-Au compounds whereas hybrids shift the d-band towards negative energies and account for the complex d-d hybridization more accurately.