Pressure induced magnetic, electronic and mechanical properties of SmX (X = Se, Te).

The magnetic, structural, elastic and electronic properties of Sm-chalcogenides in the stable [Formula: see text] and high pressure [Formula: see text] phase have been analyzed using an ab initio pseudo-potential method with a spin-polarized GGA based on exchange-correlation energy optimization, as implemented in SIESTA code. The magnetic phase stability has been determined from the total energy calculations in non-magnetic and magnetic phases, which clearly indicate that at ambient and high pressures, these compounds are ferromagnetically stable. Also, the Sm ion is described in both five and six localized f electrons. Under compression the Sm chalcogenides undergo a first-order transformation from Sm(2+) to a stable valence state (Sm(3+)) with delocalization of the 4f electrons into the 5d states of Sm followed by a structural transition from the B1 to the B2 phase. The structural properties namely, equilibrium lattice constant, bulk modulus, its pressure derivative, transition pressure and volume collapse agree well with the experimental results. We have also computed the electronic structure at different volumes.