Abstract
Semiconducting glassy chalcogenides (ChGs) have broad technological applications owing to the ability to tune their band gap through composition change. However, there is a lack of theoretical models predicting the band gap in ternary and quaternary compounds of these amorphous materials which are the most industrially used. After a critical review of some existing models concerning mainly binary compounds, we propose new possible ways of predicting the band gap depending on the proportion of existing bonds and the overall compound electronegativity difference estimated by the chemical bond approach (CBA). Confrontation with published experimental data of about 40 compounds is then given. In the analysed compounds, we find that the frequently used equation based on the band gaps of the constituent elements is not predictive unless corrected by the overall electronegativity difference. However, a newly proposed equation based on the contribution of existing bonds predicts well the band gaps in networks with relatively high rigidity. Furthermore, an added correction taking into account the contribution of the overall electronegativity difference provides an explanation of the observed bowing in the curve of band gap versus composition. In all the studied compounds, the theoretical estimation of band gaps has an error of less than 10%.