A THEORETICAL-STUDY ON THE PRESSURE-DEPENDENCE OF THE BAND-GAP IN A(I)B(III)C(2)(VI) COMPOUNDS

The self-consistent scalar relativistic band structure for AgGaX2 (X = S, Se, Te) performed in chalcopyrite structure using the TBLMTO metho d at various pressures are reported here. Empty spheres were introduce d in the calculations as the chalcopyrite structure is loosely packed. From the total energy calculations, the equilibrium lattice constant and the bulk modulus at zero pressure were calculated and these values agree well with the reported experimental values. All these compounds are found to have direct energy gap at ambient pressure with the gap widening with increased pressures which are in agreement with the expe rimental results. The deformation potential, dE(g)/dP for the compound s are also reported here. The metallisation volumes are calculated and the possibility of observing superconductivity in these compounds is discussed.