Relationship between band gap and equivalent volume of electron cloud

The characteristic parameter [Formula: see text] related to bandgap [Formula: see text] is proposed ([Formula: see text] is the equivalent volume of the outermost electron cloud of molecule). [Formula: see text] values of dozens of solid media are calculated. The results show that [Formula: see text] decreases as [Formula: see text] increases. Furthermore, change behavior of [Formula: see text] with composition is studied by using [Formula: see text], and the composition characteristics of high-[Formula: see text] solid media are summarized. According to this result, [Formula: see text] can be regulated to a certain extent by adjusting the composition. Importantly, connection among refractive index [Formula: see text], [Formula: see text] and [Formula: see text] is revealed: [Formula: see text] has both a major contribution to [Formula: see text] and a decisive effect on [Formula: see text]. These results help to promote the development of new semiconductor materials.