Eur. Phys. J. B (2012) 85: 325
https://doi.org/10.1140/epjb/e2012-30384-7

Regular Article

Electronic and magnetic properties of NiS₂, NiSSe and NiSe₂ by a combination of theoretical methods

¹ Institut für Physik, Universität Augsburg, D-86135 Augsburg, Germany
² Nano-Bio Spectroscopy Group and ETSF Scientific Development Center, Dpto. Física de Materiales, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Universidad del País Vasco UPV/EHU, Avenida Tolosa 72, E-20018 San Sebastián, Spain

^a e-mail: matteo.gatti@ehu.es

Received: 15 May 2012
Received in final form: 10 July 2012
Published online: 24 September 2012

Abstract

We investigate the electronic and magnetic properties of NiS₂, which, by varying the chemical composition substituting S by Se atoms or applying pressure, can be driven across various electronic and magnetic phase transitions. By combining several theoretical methods, we highlight the different role played by the chalcogen dimers and the volume compression in determining the phase transitions, through variations of the chalcogen p bonding-antibonding gap, the crystal-field splitting and the broadening of the bandwidths. While the generalized gradient approximation (GGA) of density-functional theory fails to reproduce the insulating nature of NiS₂, it describes well the magnetic boundaries of the phase diagram. The large GGA delocalization error is corrected to a large extent by the use of GGA + U, hybrid functionals or the self-consistent COHSEX + GW approximation. We also discuss the advantages and the shortcomings of the different approximations in the various regions of the phase diagram of this prototypical correlated compound.