Contribution à l’étude des propriétés structurales, élastiques et électroniques des composés AlX (X=N, P et As)

Abstract

The subject of this memory is the study of the structural, elastic and electronic properties of ZnS-type (B3) and NaCl-type (B1) structure in the compounds based on aluminium AlX (X = N, P and AlAs) under pressure effect, using the first-principles calculations, that are performed by employing the pseudopotential plane waves method (PP-PW) based on the density functional theory (DFT) within LDA and GGA, and as implemented in the CASTEP code. Our results show that these compounds crystallize in the zincblende phase (B3) at ambient conditions. Under the effect of the hydrostatic pressure, the AlX compounds will undergo a structural phase transition from the B3 phase to B1 phase. The elastic constants increase linearly according to the pressure. These constants verify the generalized stability criteria in the two phases and under pressure effect. The hardness of AlX compounds decrease with the increase in atomic number Z of elements X, i.e. from AlN to AlAs. The electronic properties show that the three compounds in the B3 phase and the AlN compound in the B1 phase are semiconductors and have an indirect fundamental band gap Γ → X , while AlP and AlAs in the B1 phase are metals. Under pressure effect, the nature of the fundamental band gap remainder unchanged. The density of states indicates that these compounds are partially ionic and partially covalent.