Competing Structures in (In,Ga)Se and (In,Ga)2Se3 Semiconductors
  The electronic structure of four polytypes (beta, gamma, delta and epsilon) of hexagonal GaSe and InSe is calculated from first principles, using the WIEN2k and VASP codes and PBEsol prescription for the exchange-correlation potential, aiming specifically at elucidating the crystallographic parameters and comparing the energy placement of corresponding competing structures. Further on, the compounds with different composition of the same constituents, namely the ordered-vacancies systems Ga2Se3 and In2Se3, were subject to a similar study, of which the relaxed crystal structure data for three different phases is reported. Comparison is done with the nomi- nal wurtzite structure over which the cation vacancies are introduced, and the relaxation pattern discussed. 
J. Srour, A. Postnikov, M. Badawi, F. El Haj Hassan
cond-mat.mtrl-sci