Fig. 2: Structural units in binary and ternary amorphous chalcogenides.

a Populations of structural units in the binary tellurides, a-GeTe (upper panels) and a-Sb₂Te₃ (lower panels). Representative bonding geometries of (4,1)- and (5,1)-type hypervalent units are shown. The positions of MLWF centres for hyperbond pairs, covalent bonds and lone pairs (LPs) are specified for each type of hypervalent unit. b Populations of structural units in ternary chalcogenide models of a-GSS (top panels), a-GSSe (middle panels) and a-GST (bottom panels). For a-GST, data are taken from Lee and Elliott⁴, with error bars being added. For each model, three independently-generated amorphous model structures were analysed, to obtain better statistics. The standard deviation for those model structures is represented by an error bar.