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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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Ab initio full-potential linearised augmented plane wave (FP-LAPW) method within density functional theory is applied to study the effect of composition on the structural, electronic and thermodynamic properties of CuBr x I 1−x ternary alloy. The structural properties at equilibrium are investigated by using the new form of generalised gradient approximations that are based on the optimisation of total energy. For band structure calculations, both Engel-Vosko and modified Becke-Johnson of the exchange-correlation energy and potential, respectively, are used. Deviation of the lattice constants from Vegard's law and the bulk modulus from linear concentration dependence are observed. The microscopic origins of the gap bowing were explained by using the approach of Zunger and co-workers. On the other hand, the thermodynamic stability of this alloy was investigated by calculating the excess enthalpy of mixing Hm as well as the phase diagram by calculating the critical temperatures. A numerical first-principle calculations of the elastic constants as function of pressure is used to calculate C 11 , C 12 and C 44 .