AbstractThe structural disorder model, recently proposed by the authors, for amorphous semiconductors is generalized for Se within the framework of the concept of charged dangling bond (CDB) defects, packing fraction, thermodynamic theory of defects, and the additive approximation near the crystalline to amorphous transition which is interpreted as a point of spontaneous production of CDB defects. The model is able to explain at least qualitatively the data on thermodynamic properties, the structural disorder parameterXrepresenting the ratio 〈U2〉x/〈U2〉0, and the width of the Urbach absorption edge