Clustering of Zirconium Atoms in Zr ₅ Te ₆ : A Novel NiAs‐Type‐Related Telluride with Ordered Vacancies

Abstract

Zr5Te6 has been synthesized and its structure determined by means of single crystal X-ray diffraction to be trigonal, P3m1, Z=3, Pearson symbol hP33, a = 1172.8(2) pm, c = 707.0(1) pm. Zr5Te6 adopts a metal-deficient, vacancy-ordered 3a x 3a x 1c superstructure of the NiAs type structure. In the Zr atom layers, alternately one and two out of nine Zr atoms are missing. The less densely populated layers (7/9) consist of star-shaped Zr7 clusters with intracluster contacts of 351.1 pm; the shortest Zr-Zr intercluster distance is 470.5 pm. In the more densely populated Zr atom layers (8/9), three quarters of the Zr atoms are arranged to pairs (326.4 pm). The distinctive distribution of the vacancies affords a topologically uniform fivefold Zr coordination (283.5 - 302.6 pm) for all three crystallographically inequivalent Te atoms. They are shifted towards the vacancies in the Zr atom layers. The associated corrugation of the Te atom layers is characterized by an amplitude of 28 pm. The Te-Te contacts are > or =368.1 pm. According to extended Hückel calculations, the defects in the Zr atom layers lead to a reduction in overall Zr-Te bonding interactions relative to ZrTe (NiAs). However, through the clustering the total attractive intralayer Zr-Zr interactions increase considerably, thus providing decisive stabilization of the structure. As revealed by thermal analyses, Zr5Te6 undergoes a reversible phase transition at 1,513 +/- 5 K. On the Zr-rich side, Zr5Te6 coexists with ZrTe (WC), and, above 1,438 +/- 5 K with the hitherto unknown ZrTe (MnP). Zr5Te6 exhibits temperature independent paramagnetic properties (chimol = 0.7 x 10(-3) cm3 mol(-1)) that are typical for a metallic conductor. An abrupt increase in the magnitude of the diamagnetic susceptibility below 2.2 K in a weak magnetic field indicates a superconducting transition.

Structure, Properties, and Bonding of ZrTe (MnP Type), a Low-Symmetry, High-Temperature Modification of ZrTe (WC Type)

“…In the zigzag chains, which extend parallel to [010], the shortest Zr−Zr distances in the structure are found, 326.0 pm. This distance is comparable to the shortest Zr−Zr distance in Zr 5 Te 6 (326.4 pm) . The second Zr−Zr contact inside the chains amounts to 377.2 pm, almost identical to the Zr−Zr distance in the hexagonal planes in ZrTe ( WC ).…”

“…The influence of the d-electron count on clustering in chalcogenides of the valence electron poor transition metals, including some zirconium tellurides, has been discussed elsewhere . The arrangement of the metal atoms to zigzag chains is typical for phases with a d 2 metal atom electron configuration.…”

“…In recent years, a number of new phases have been discovered in the system Zr−Te. In the metal-rich part of the system, Zr 3 Te and Zr 2 Te were characterized, whereas on the tellurium-rich side, Zr 5 Te 6 and Zr 1.3 Te 2 were identified. Furthermore, a reinvestigation of the phase diagram was carried out lately …”

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“…35 Zr 5 Te 6 has a metal-deficient vacancy-ordered version of the NiAs structure. 36 In situ time-resolved neutron diffraction has been applied to studies of the hydrothermal synthesis of BaTiO 3 . 37…”

Structural, mechanical, and electronic properties of Zr – Te compounds from first-principles calculations

“…In order to offer a comparative study between Zr-Te compounds, the fundamental properties of ZrTe, ZrTe 3 , ZrTe 5 , Zr 2 Te, Zr 3 Te, Zr 5 Te 4 , and Zr 5 Te 6 [17][18][19][20][21][22][23][24][25] are investigated by using the first-principles calculations, which include structural, elastic, mechanical, and electronic properties.…”