Eur. Phys. J. B (2015) 88: 177
https://doi.org/10.1140/epjb/e2015-60005-x

Regular Article

Structural and electronic properties of MX₃ (M = Ti, Zr and Hf; X = S, Se, Te) from first principles calculations

The National Institute for Theoretical Physics, School of Physics and Mandelstam Institute for Theoretical Physics, University of the Witwatersrand, Johannesburg, Wits 2050, South Africa

^a e-mail: mahmudaaa@yahoo.co.uk

Received: 4 January 2015
Received in final form: 17 March 2015
Published online: 8 July 2015

Abstract

The structural and electronic properties of layered TiS₃, TiSe₃, TiTe₃, HfS₃, HfSe₃, HfTe₃, ZrS₃, ZrSe₃ and ZrTe₃ with structure P2₁/m have been investigated using density functional theory for the first time at the atomic level within the vdW-DF and vdW-TS approximations to account for long range dispersive forces, which is important in predicting layered material interlayer spacing accurately. To get reasonable estimates of the band gaps, MBJ band structure calculations were performed. With exception of the tellurides and TiSe₃, which are found to be metallic, the compounds are indirect band gap semiconductors with band gap in the range of 0.44 to 2.04 eV. The minimum direct band gaps were found to be in a similar range. The elastic constants of these structures confirm their mechanical stability by satisfying all the stability criteria for monoclinic structures. Phonon band structure and thermal properties were calculated using density functional perturbation theory. The phonon dispersion relations show that the structures are stable under small atomic displacements.