STRUCTURAL AND BONDING PROPERTIES OF SOLID TELLURIUM FROM 1ST-PRINCIPLES CALCULATIONS

We have studied the structural and bonding properties of the equilibrium and high-pressure phases of tellurium by means of first-principles total-energy calculations, performed within the local-density approximation. The calculated characteristics of the various polymorphs under pressure show good general agreement with existing experiments. However, some systematic discrepancies occur between computed and measured structural parameters for the open linear-chain (trigonal) and layer-type (orthorhombic) phases. The interchain and interlayer distances are underestimated within the local-density approach, and the relative stability of the trigonal and of the orthorhombic phase with respect to compact metallic structures is lower in the calculations than indicated by the experimental phase diagram. The complex structural changes of Te under pressure are discussed in terms of the trends under pressure of the different types of bonds involved in the various crystal structures.