Ab initio investigations of calcium chalcogenide alloys

• Published in: Journal of alloys and compounds 2009-10, Vol.485 (1), p.642-647
• Main Authors: Slimani, M., Meradji, H., Sifi, C., Labidi, S., Ghemid, S., Hannech, E.B., El Haj Hassan, F.
• Format: Article
• Language: English
• Subjects: Bowing gap; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Critical temperature; Cross-disciplinary physics: materials science; rheology; Electron states; Exact sciences and technology; FP-LAPW; Materials science; Methods of electronic structure calculations; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase diagrams of metals and alloys; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2009.06.104

Full potential-linearized augmented plane wave (FP-LAPW) method within density functional theory (DFT) was applied to study the structural, electronic, optical and thermodynamic properties of CaS 1− x Te x , CaSe 1− x Te x and CaS 1− x Se x ternary alloys. In this approach the generalized gradient approximation (GGA) was used for the exchange-correlation potential. Moreover, the alternative form of GGA proposed by Engel and Vosko (EVGGA) was also used for band structure calculations. The effect of composition on lattice constant, bulk modulus, band gap, refractive index, and dielectric function was investigated. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. In order to investigate the thermodynamic stability of the alloys we first calculated the excess enthalpy of mixing Δ H m as a function of concentration ( x). Then by using a regular model solution the x-dependent interaction parameter, Ω was obtained from the result of Δ H m versus x. Finally, the phase diagram of the alloys was calculated. Finally, the phase diagram of the alloys was obtained.