Journal of the American Chemical Society, Vol.123, No.18, 4168-4173, 2001
Structure, properties, and bonding of ZrTe (MnP type), a low-symmetry, high-temperature modification of ZrTe (WC type)
ZiTe (MnP) was synthesized by high-temperature methods at 1570 K in Ta ampules. The structure of the telluride was determined by means of single-crystal X-ray diffraction to be orthorhombic, Pnma (No. 62), Z = 4, Pearson Symbol oP8, a = 739.15(15) pm, b = 377.23(8) Fm, c = 694.34(14) Fm. The orthorhombic MnP type structure is a distorted variant of the. NiAs type structure with pronounced metal-metal zigzag chains. Zigzag chains are typical for phases with a d(2) metal atom electron configuration. According to extended Huckel calculations, the homonuclear interactions in the zigzag chains make up for 2/3 of the Zr-Zr interactions in ZrTe (MnP) and contribute decisively to the stability of the structure. The emergence of the distorted MnP type structure instead of the high-symmetry NiAs type ZrTe at high temperatures can be understood as the result of an optimization of homonuclear Zr-Zr interactions arising from states close to the Fermi level. The hexagonal WC. type ZrTe transforms above 1438 +/- 5 Ii into ZrTe (MnP) (DeltaH = 8.3 +/- 1.0 kJ mol(-1)). The phase transition is reversible, although at room-temperature the reverse reaction is kinetically inhibited. Zr-5-Te-4 and Zr5Te6 are the phases nest to ZrTe. ZrTe (MnP) exhibits temperature-independent paramagnetic properties (chi (mol) = 0.14 x 10(-3) cm(3) mol(-1)), as typical for a metallic conductor. Resistivity measurements on ZtTe (MnP) imply metallic behavior.