Atomic networks and clustering in liquid Te and K–Te alloys

Ab initio molecular dynamics studies of the structural and electronic properties of liquid Te and tellurium-rich K–Te alloys are presented. Our work was done on pure l-Te at 748 and 1123 K, on the K12Te88-alloy at 723 K and at the equiatomic composition at 770 K. Our research has shown that the Te-chains are disturbed by threefold co-ordinated Te atoms forming bridges between the chains and onefold co-ordinated marking chain-ends. As the occurrence of these `defects' is very large (∼20% each type) liquid tellurium is better described as an atomic network. On adding a small amount of potassium (12%) the dangling bonds are saturated, stabilizing the chain-like structure. Equiatomic K–Te shows a different picture. Due to the charge transfer from K to Te the Te− atoms are isoelectronic to iodine, forming polyanionic clusters. As in the crystalline phase Te2 dumbells are built. Additionally one can find isolated Te atoms as well as short chains consisting of three or four atoms.