Investigation of the pressure dependence of band gaps for silver halides within a first-principles method

摘要

The pressure dependence of the direct and indirect band gaps in rocksalt silver halides has been studied using the full-potential linearized augmented plane wave method within the generalized gradient approximation for the exchange-correlation potential. It is found that indirect band gaps (L → X and L → Γ) exhibit different responses to application of pressure. Similar trends are found for the indirect band gaps of AgCl and AgBr while the trend in AgI (L → Γ) band gap is different. In all the compounds, the effect of pressure on the direct band gaps (Γ → Γ, X → X and L → L) show qualitatively similar results. The fundamental indirect band gap (L → Γ) pressure coefficients are - 4.19 meV (GPa)~(-1) and - 3.81 meV (GPa)~(-1) for AgCl and AgBr while for AgI (L → X) it is - 61.50 meV (GPa)~(-1). The band gap pressure coefficient as well as the volume deformation potential for the various band gaps of the compounds have also been investigated.