الخلاصة:
The strurural, electronic and elastic properties of rare-earth monochalcogenides EuX (X=Se,
Te) were investigated with the full-potential-linearized-augmented plane wave (FP-LAPW)
based on density functional theory (DFT). The exchange-correlation term is treated using two
approximations the generated gradient approximation (GGA) and the local density
approximation (LDA). The structural parameters, such as the equilibrium lattice parameters,
the bulk modulus B and its derivative B‘, the electronic proprerties (the band structure, the
total density) and the elastic constants (C11, C12, C44) of EuX compounds (X= Se, Te) are
calculated in two phases: face-centered cubic structure type NaCl (B1) and the simple cubic
structure CsCl type (B2) under ambient and high pressure. We also studied the structural
phase transition between B1, B2. To determine this transition pressure, we calculated Gibbs
energy G= E+PV-TS
