In this work, we study the phase stability and electronic properties of silver halides ( AgBr, AgCl and AgI) using the full-potential linearized augmented plane wave method within the density functional theory. In this approach, the WuÀCohen generalized gradient approximation was used for the exchangeÀcorrelation potential. Moreover, the modified BeckeÀJohnson approximation was also used for bandstructure calculations. Various structural phase transitions were considered here in order to confirm the most stable structure and to predict the phase transition under hydrostatic pressure. In addition, we have studied the band structures of the stable phases of these compounds which reveal that the three compounds exhibit semiconducting behavior. The results obtained are compared with other calculations and experimental measurements.

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Abstract:Structural, electronic and thermal properties of Zn 1− Mg S ternary alloys are studied by using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). The Wu-Cohen generalized gradient approximation (WC-GGA) is used in this approach for the exchangecorrelation potential. Moreover, the modified Becke-Johnson approximation (mBJ) is adopted for band structure calculations. The dependence of the lattice constant, bulk modulus and band gap on the composition x showed that the first exhibits a small deviation from the Vegard's law, whereas, a marginal deviation of the second from linear concentration dependence (LCD). The bowing of the fundamental gap versus composition predicted by our calculations agrees well with the available theoretical data. The microscopic origins of the gap bowing are explained by using the approach of Zunger and co-workers. Thermal effects on some macroscopic properties of Zn 1− Mg S alloys are also investigated using the quasi-harmonic Debye model, in which the phononic effects are considered. As, this is the first quantitative theoretical prediction of the thermal properties of Zn 1− Mg S alloys, no other calculated results and furthermore no experimental studies are available for comparison. 64.75.-q, 65.40.-b, 71.20.-b, 81.90.+c PACS (2008):