First principle investigation into hexagonal and cubic structures of Gallium Selenide

All-electron self consistent Full Potential Linearised Augmented Plane Waves (FP-LAPWs) method mixed with APW + lo and Local Orbital (LO) alternatives within generalised gradient density approximation is used to study crystalline Gallium Selenide (GaSe) in the rock salt (B1), CsCl (B2), Zinc blende (B3), Wurtzite (B4), β(D6h4) and ε(D3h1) structures. Bulk properties such as equilibrium lattice constants, bulk modulus and its pressure derivative in these phases are determined and compared to available experimental and theoretical data.Our calculations show that the III–VI GaSe semiconductor compound exhibits a slight preference to crystallize at zero pressure in ε(D3h1) structure rather than in β(D6h4) structure; and under appropriate pressures, phase transitions occur toward NaCl (B1) cubic phase. The elastic constants are calculated for all these structures and compared with available previous results. The stability of GaSe in the rock salt (B1), CsCl (B2), Zinc blende (B3), Wurtzite (B4), β(D6h4) and ε(D3h1) structures is then determined, followed by an electronic structure investigation.

► ε(D3h1) and β(D6h4) GaSe types are both zero pressure phases.
► Under appropriate pressure phase transitions occur toward NaCl (B1) type.
► CsCl (B2) and Zinc blende (B3) GaSe phases are unstable.
► The NaCl (B1) and Wurtzite (B4) GaSe phases exhibit a metallic behaviour.