Electronic and magnetic properties of NiS2, NiSSe and NiSe2 by a combination of theoretical methods Cosima Schuster, Matteo Gatti and Angel Rubio Eur. Phys. J. B, 85 9 (2012) 325 Published online: 24 September 2012 DOI: 10.1140/epjb/e2012-30384-7