Network disruption and modification in arsenic and germanium chalcogenides by the addition of univalent metal sulfides and selenides: Comparisons with network disruption and modification in zirconium silicate alloys

The addition of the tetravalent metal oxide, ZrO2, into non-crystalline (nc-) SiO2 to form thin film nc-Zr silicates, and the univalent metal sulfides (selenides), (Cu,Ag)2S(Se), into nc-As2S(Se)3 and -GeS(Se)2 networks to form nc-thin film and/or bulk Ag and Cu chalcogenide alloys are compared. The bonding coordination of representative metal-atoms, generally (i) 4 for Cu, (ii) 3 for Ag, and (ii) up to 8 for Zr, do not obey the Mott 8-N rule bonding for the Si, Ge, As, and O and chalcogenide atoms in their respective host networks. These break-downs of 8-N bonding for metal atoms are accompanied by increases in the coordination of O-atoms from 2 to 3 in Zr silicate alloys to accommodate increased bond ionicity, and increases of 2–4 for S(Se)-atoms in Ag and Cu chalcogenide alloys to accommodate covalent bonding requirements in tetrahedral arrangements.