Studies regarding the homogeneity range of the zirconium phosphide telluride Zr_(2+δ)PTe_2

摘要

The phosphide tellurides Zr_(2+δ)PTe_2 (0 < δ < 1) can be synthesized from the elements in a solid state reaction or by thermal decomposition of Z. Zr_2PTe_2 decomposes under release of Te_2(g) + P_4(g) forming the homogeneity range Zr_(2+δ)PTe_2 The growth of single crystals of Zr_(2+δ)PTe_2 succeeded by chemical vapour transport using iodine as transport agent from 830 °C in direction of higher temperatures up to 900 °C. Zr_(2+δ)PTe_2 crystallizes in the rhombohedral space group R3m (no. 166) with lattice parameters a = 383(1)...386(1) pm and c = 2935(4)...2970(4) pm for δ = 0...1, respectively. Single crystal data have been determined for Zr_(2.40)(2)PTe_2 with lattice parameters a = 385.24(4) pm and c = 2967.8(4) pm.The electronic structure and chemical bonding in Zr_(2+δ)PTe_2 was investigated by the linear muffin-tin orbital (LMTO) method. Both Zr_2PTe_2 and Zr_3PTe2 show non-vanishing DOS values at the Fermi level (E_f) indicating metallic character. According to COHP bonding analyses, mainly the heteroatomic Zr-P and Zr-Te bonds are responsible for the structural stability of Zr_3PTe_2. The new Zr2-Te bond, which is not present in Zr2PTe2, is stronger than Zr1-Te and is thought to be responsible for the stability of phases having Zr in excess.