In this piece of research, we have performed self-consistent ab-initio calculations to study thernstructural and e lectronic properties of BexZnl -xS mixed crystals in the various low and highrnpressure crystallographic phases of thc alloy. The zinc blend phase and rock salt phase ofrncompositionally variant zinc-bery llium-sulfide have been used for the calc ul ations of' structura lrnand electronic properties within the local density approximation of density fu nctional theory. Thernconcent rat ion of Be (X) changes f'rom 0.00, 0.41 , and 0.66 to 1.00 in the al loy. Super cells (54rnatoms) of the all oys are constructed and fully relaxed. Al l the values of ternary and binary alloyrnlattice constants, bulk modulus and cnergy band gap are calculated on these relaxed structures.rnOur results are comparable to the contemporary theoreti cal and experimental observations. Ourrnvalues for the structural parameters obtained in the LOA approximation are also in goodrnagreement with the experimental values. We have also observed direct band to indirect band gaprn(r ..... r) ..... (r ..... X) by increasi ng beryl lium concentrations along with some LOA related underrnestimation s of gap widt hs. For al l the samples of the alloy, high pressure phase tran sitions arernfound to present and reported in the range of' giga pascal pressures. At the same time, increase ofrnhardening of the al loy is reported due to Be content and the bulk modulus correspondinglyrnincreases in the alloy. We have also analyzed the concentration related effects on electronicrndensity of states and bowing parameters.