12067-76-4Relevant articles and documents
Crystal structure of WI4
Yarovoi,Smolentsev,Ermolaev,Mironov
, p. 199 - 201 (2016)
Tungsten tetraiodide WI4 (1) is produced by a high-temperature reaction of WTe2 and I2 in a vacuum sealed ampoule. The crystals of 1 belong to the triclinic crystal symmetry, space group P-1, Z = 4, a = = 7.9291(3) ?, b = 10.7695(4) ?, c = 10.8117(4) ?, α = 85.668(1)°, β = 71.772(1)°, γ = 71.559(1)°, V = = 831.60(5) ?3, d calc = 5.523 g/cm3. The structure of 1 consists of tetrameric W4I16 molecules in which W atoms are in a distorted octahedral environment formed by I atoms.
Thermodynamic properties of tungsten ditelluride (WTe2). I. The preparation and low-temperature heat capacity at temperatures from 6 K to 326 K
Callanan, Jane E.,Hope, G. A.,Weir, Ron D.,Westrum, Edgar F.
, p. 627 - 638 (1992)
The heat capacity of the dichalcogenide: tungsten ditelluride, WTe2, was measured over the temperature range 5.5a phase transition is not present.However, an anomalous rise in the molar heat capacity Cp,m occurs in the region 92m = (0.10+/-0.02)*R.The anomaly coincides with the temperature range where all the translational, librational, and internal vibrational modes become fully excited.The electronic molar heat capacity Tγm = (5.99+/-1.83)mJ*K-1*mol-1 and for the lattice, the Debye characteristic temperature ΘD = (133.8+/-0.6) K.Standard molar thermodynamic functions are presented at selected temperatures from 5 K to 335 K.
Reversible Iodine Intercalation into Tungsten Ditelluride
Schmidt, Patrick,Schneiderhan, Philipp,Str?bele, Markus,Romao, Carl P.,Meyer, Hans-Jürgen
, p. 1411 - 1418 (2021)
The new compound WTe2I was prepared by a reaction of WTe2 with iodine in a fused silica ampule at temperatures between 40 and 200 °C. Iodine atoms are intercalated into the van der Waals gap between tungsten ditelluride layers. As a result, the WTe2 layer separation is significantly increased. Iodine atoms form planar layers between each tungsten ditelluride layer. Due to oxidation by iodine the semimetallic nature of WTe2 is changed, as shown by comparative band structure calculations for WTe2 and WTe2I based on density functional theory. The calculated phonon band structure of WTe2I indicates the presence of phonon instabilities related to charge density waves, leading to an observed incommensurate modulation of the iodine position within the layers.
Synthesis of Semiconducting 2H-Phase WTe2Nanosheets with Large Positive Magnetoresistance
Lei, Feng-Cai,Li, Dong-Sheng,Li, Shuang,Peng, Xu,Wang, Ruo-Qi,Wu, Ya-Pan,Xie, Jun-Feng
, p. 11935 - 11939 (2020)
Tungsten ditelluride (WTe2) is provoking immense interest because of its unique electronic properties, but studies about its semiconducting hexagonal (2H) phase are quite rare. Herein, we report the synthesis of semiconducting 2H WTe2 nanosheets with large positive magnetoresistance, for the first time, by a simple lithium-intercalation-assisted exfoliation strategy. Systematic characterizations including high-resolution transmission electron microscopy, X-ray diffraction, and Raman and X-ray photoelectron spectroscopies provide clear evidence to distinguish the structure of 2H WTe2 nanosheets from the orthorhombic (Td) phase bulk counterpart. The corresponding electronic phase transition from metal to semiconductor is also confirmed by density of states calculation, optical absorption, and electrical transport property measurements. Besides, the 2H WTe2 nanosheets exhibit large positive magnetoresistance with values of up to 29.5% (10 K) and 16.2% (300 K) at 9 T. Overall, these findings open up a promising avenue into the exploration of WTe2-based materials in the semiconductor field.
A New Modification of TeI4 Possessing the Crystal Structure Proposed for WI4
Schneiderhan, Philipp,Schmidt, Patrick,Str?bele, Markus,Romao, Carl P.,Meyer, Hans-Jürgen
, p. 3780 - 3784 (2020)
A modification of TeI4 (ζ-TeI4) was discovered in an attempt to reproduce a reported synthesis of WI4, beginning from WTe2 and iodine. The crystal structure of ζ-TeI4 was solved from single-crystal data in the triclinic space group P1, isotypic with the structure of the previously reported WI4. The crystal structure of ζ-TeI4 contains isolated tetrameric Te4I16 molecules, in which tellurium atoms are coordinated by six iodine atoms. Electron microprobe and ICP-OES measurements confirm the identity of the new phase and make the formation of WI4 via this synthesis route implausible. A comparison of ζ-TeI4 with all other TeI4 polymorphs is drawn by DFT calculations and structural relationships. Special conditions regarding the formation of ζ-TeI4 as well as the phase transition from δ-TeI4 into ζ-TeI4 are reported.
