Abstract

Optical measurements were carried out on bulk glasses Ge_xSe_1-x(x = 10, 17, 22, 25, 33). The direct band gap values were determined from the experimental data. Theoretical model is introduced which fits on the data. Compositional dependent power (p = 0.03) on band gap data across the Ge_xSe_1-x series is determined. Duffy’s relation is also explored to estimate the optical energy band gap which fairly matches with experimental band gap. Correlation graph between optical energy band gap (E_g) and (1-R_M/V_M) shows a new relationship E_g = 7.58(1- R_M/V_M)^1.08. We are introducing the new concept of modified compactness for covalent glasses and composition dependent compactness across Ge_xSe_1-x glasses are understood. Physical parameters were also obtained such as chemical bond energy modification and cross-linking density (rigidity) in order to support the explanation of the optical band gap.

Keywords:Chalcogenide glasses; Rigidity; Band gap; Bond energy; Compactness; Model