Pressure dependent ground state, elastic and thermo physical properties of Europium and Lanthanum mixed alloy chalcogenides Eu_xLa_1-xS (x = 0, 0.45, 0.85, 1)

The pressure dependent elastic, mechanical and thermo physical properties of rock salt (B1) to CsCl (B2) structures in Europium chalcogenides Eu_xLa_1-xS (x = 0, 0.45, 0.85, 1) are presented using model inter-atomic potential with inclusion of zero point energy. As the doping concentration of Europium increases transition pressure decreases with large volume collapse. Calculated transition pressure for EuS, Eu_0.45La_0.55S, Eu_0.85La_0.15S, LaS are 21.5GPa, 25.6GPa, 23.6GPa, 27.5GPa respectively. Furthermore the increment in doping concentration of Europium leads the material Eu_xLa_1-xS (x = 0, 0.45, 0.85, 1) towards more brittle nature Enhancement in Debye Temperature (θ_D) in B1 phase at higher pressure indicates the mechanical stiffening of lattice. Pugh's and Poisson's ratio indicate brittle nature of material EuxLa_1-xS (x = 0, 0.45, 0.85, 1). The present results are in general in good agreement with experimental and other theoretical technique available for the end point members (x = 0 and x = 1). (author)