- Crystal structure of WI4
-
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.
- Yarovoi,Smolentsev,Ermolaev,Mironov
-
-
Read Online
- Pressure-Induced Phase Transition in Weyl Semimetallic WTe2
-
Tungsten ditelluride (WTe2) is a semimetal with orthorhombic Td phase that possesses some unique properties such as Weyl semimetal states, pressure-induced superconductivity, and giant magnetoresistance. Here, the high-pressure properties of WTe2 single crystals are investigated by Raman microspectroscopy and ab initio calculations. WTe2 shows strong plane-parallel/plane-vertical vibrational anisotropy, stemming from its intrinsic Raman tensor. Under pressure, the Raman peaks at ≈120 cm?1 exhibit redshift, indicating structural instability of the orthorhombic Td phase. WTe2 undergoes a phase transition to a monoclinic T′ phase at 8 GPa, where the Weyl states vanish in the new T′ phase due to the presence of inversion symmetry. Such Td to T′ phase transition provides a feasible method to achieve Weyl state switching in a single material without doping. The new T′ phase also coincides with the appearance of superconductivity reported in the literature.
- Xia, Juan,Li, Dong-Fei,Zhou, Jia-Dong,Yu, Peng,Lin, Jun-Hao,Kuo, Jer-Lai,Li, Hai-Bo,Liu, Zheng,Yan, Jia-Xu,Shen, Ze-Xiang
-
-
Read Online
- Thermodynamic properties of tungsten ditelluride (WTe2). I. The preparation and low-temperature heat capacity at temperatures from 6 K to 326 K
-
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.
- Callanan, Jane E.,Hope, G. A.,Weir, Ron D.,Westrum, Edgar F.
-
-
Read Online
- Metal-metal vs Tellurium-tellurium bonding in WTe2 and its ternary variants TaIrTe4 and NbIrTe4
-
The new ternary transition-metal tellurides TaIrTe4 and NbIrTe2 are ordered variants of the WTe2 structure, which in turn is based on a distortion of the CdI2-type layered structure. The layers in WTe2 consist of buckled sheets of Te atoms, with the metal atoms residing in distorted octahedral sites. Through single- crystal X-ray diffraction methods, the structure of TaIrTe4 has been determined and that of WTe2 has been redetermined. The compounds TaIrTe4 and WTe2 belong to space group C207Pmn21 of the orthorhombic system with four formula units in cells of dimensions a = 3.770 (1), b= 12.421 (6), and c = 13.184 (6) ? and a = 3.477 (2), b = 6.249 (4), and c = 14.018 (9) ?, respectively, at 113 K. While metal-metal bonding is a structural feature common to all three compounds, Te-Te bonding is observed only in the ternary compounds. The trends of increasing metal-metal and decreasing Te-Te distances on progressing from WTe2 to TaIrTe4 and NbIrTe4 have been rationalized by electronic band (extended Hückel) calculations. These trends are related to the creation of Te-Te bonds, ensuring the stability of the WTe2 structure type even when addition of more d electrons leads to a weakening of metal-metal bonds. This concept is generalized to an entire series of compounds MM′Te4 (M = Nb, Ta; M′ = Ru, Os, Rh, Ir).
- Mar, Arthur,Jobic, Stéphane,Ibers, James A.
-
-
Read Online
- Reversible Iodine Intercalation into Tungsten Ditelluride
-
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.
- Schmidt, Patrick,Schneiderhan, Philipp,Str?bele, Markus,Romao, Carl P.,Meyer, Hans-Jürgen
-
-
Read Online
- Synthesis and reactivity of W3Te74+ clusters and chalcogen exchange in the M3Q7 (M = Mo, W; Q = S, Se, Te) cluster family
-
Heating WTe2, Te, and Br2 at 390°C followed by extraction with KCN gives [W3Te7(CN)6] 2-. Crystal structures of double salts Cs3.5K{[W 3Te7(CN)6]Br}Br1.5·4.5H 2O (1), Cs2K4{[W3Te 7(CN)6]2Cl}Cl·5H2O (2), and (Ph4P)3{[W3Te7-(CN) 6]Br}·H2O (3) reveal short Te2...X (X = Cl, Br) contacts. Reaction of polymeric Mo3Se7Br 4 with KNCSe melt gives [Mo3Se7(CN) 6]2-. Reactions of polymeric Mo3S 7Br4 and Mo3Te7I4 with KNCSe melt (200-220°C) all give as final product [Mo3Se 7(CN)6]2- via intermediate formation of [Mo3S4Se3(CN)6]2-/ [Mo3SSe6(CN)6]2- and of [Mo 3Te4Se3(CN)6]2-, respectively, as was shown by ESI-MS. (NH4)1.5K 3{[Mo3Se7(CN)6]I}I 1.5·4.5H2O (4) was isolated and structurally characterized. Reactions of W3Q7Br4 (Q = S, Se) with KNCSe lead to [W3Q4(CN)9]5-. Heating W3Te7Br4 in KCNSe melt gives a complicated mixture of W3Q7 and W3Q4 derivatives, as was shown by ESI-MS, from which E3[W 3(μ3-Te)(μ-TeSe)3(CN)6] Br·6H2O (5) and K5[W3(μ3- Te)(μ-Se)3(CN)9] (6) were isolated. X-ray analysis of 5 reveals the presence of a new TeSe2- ligand. The complexes were characterized by IR, Raman, electronic, and 77Se and 125Te NMR spectra and by ESI mass spectrometry.
- Sokolov, Maxim N.,Abramov, Pavel A.,Gushchin, Artem L.,Kalinina, Irina V.,Naumov, Dmitry Y.,Virovets, Alexander V.,Peresypkina, Eugenia V.,Vicent, Cristian,Llusar, Rosa,Fedin, Vladimir P.
-
-
Read Online
- Synthesis of Semiconducting 2H-Phase WTe2Nanosheets with Large Positive Magnetoresistance
-
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.
- Lei, Feng-Cai,Li, Dong-Sheng,Li, Shuang,Peng, Xu,Wang, Ruo-Qi,Wu, Ya-Pan,Xie, Jun-Feng
-
-
Read Online
- Layered Transition-Metal Ditellurides in Electrocatalytic Applications - Contrasting Properties
-
The layered compounds and especially transition-metal dichalcogenides are at the forefront of current research on electrocatalytic materials. Despite the fact that electrocatalytical properties of molybdenum and tungsten disulfides are well-known, their tellurium analogues are significantly less explored. Here we show an effective method for MoTe2 and WTe2 chemical exfoliation based on alkali metal intercalation and subsequent reaction with water. The as-synthesized and exfoliated tellurides were characterized in detail and investigated for potential application in electrocatalysis. The inherent electrochemical activity related to both cation and anion was observed. This is dominantly related to the oxidation tendency of tellurium. The MoTe2 and WTe2 show significantly contrasting properties toward the hydrogen evolution reaction, where MoTe2 shows highly increased HER activity with little dependence on electrochemical treatment, whereas WTe2 shows slightly worse improvement and strong dependence on the electrochemical treatment. In particular, the exfoliated MoTe2 exhibits improved electrocatalytic activity for hydrogen evolution reaction and possesses a huge application potential.
- Luxa, Jan,Vosecky, Pavel,Mazánek, Vlastimil,Sedmidubsky, David,Pumera, Martin,Lazar, Petr,Sofer, Zdenek
-
-
Read Online
- A New Modification of TeI4 Possessing the Crystal Structure Proposed for WI4
-
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.
- Schneiderhan, Philipp,Schmidt, Patrick,Str?bele, Markus,Romao, Carl P.,Meyer, Hans-Jürgen
-
-
Read Online
- New lithium- And ethylenediamine-intercalated superconductors Lix(C2H8N2)yWTe2
-
We have successfully synthesized new superconductors Lix(C2H8N2)yWTe2 with 0 2. It has be
- Harada, Mimori,Kato, Masatsune,Kawamata, Takayuki,Noji, Takashi,Ono, Masato,Sato, Kazuki
-
-
- Solid-state tellurium-125 nuclear magnetic resonance studies of transition-metal ditellurides
-
Solid-state 125Te NMR studies of inorganic compounds containing tellurium in oxidations states ranging from -II to VI have been made. The chemical shift tensors of Te(OH)6, TeCl4, TeO2 and elemental tellurium ha
- Orion, Isabelle,Rocha, Joao,Jobic, Stephane,Abadie, Virginie,Brec, Raymond,Fernandez, Christian,Amoureux, Jean-Paul
-
p. 3741 - 3748
(2007/10/03)
-
- Diphenylditellurium Binuclear Complexes with Chromium and Tungsten Pentacarbonyls: Synthesis, Molecular Structure, and Thermal Decomposition
-
Photochemical reactions of M(CO)6 (where M is W or Cr) and Ph2Te2 taken in a 2 : 1 molar ratio in tetrahydrofuran at room temperature, or reactions of (CO)5M(thf) with Ph2Te2 yield dark lilac binuclear complexes [(CO)5M]2(μ-Te2Ph2), where M=Cr (3) or M=W (4). The reaction of (CO)5Cr(Te2Ph2) with (CO)5W(thf) yields the heterometal complex (CO)5Cr(μ-Te2Ph2)W(CO)5 (5). The structure of 3-5 is determined by X-ray crystallography. The Te-Te bond (up to 2.812(2), 2.808(2), and 2.828(2) A?, respectively) becomes significantly longer upon formation of shortened M-Te bonds in 3 and 4 (2.656(3) and 2.779(2) A?, respectively). A study of thermal decomposition of 3-5 in comparison with mononuclear complexes (CO)5M(Te2Ph2), where M is Cr or W (1 or 2, respectively), proved the exothermicity of consecutive elimination of carbonyl and phenyl groups (at 145-170 and 177-234°C, respectively), to give tellurides MTe as the final products (intermediate ditellurides MTe2 formed from mononuclear complexes 1 and 2 eliminate one tellurium atom at 268 and 242°C, respectively).
- Pasynskii,Torubaev,Eremenko,Vegini,Nefedov,Dobrokhotova,Yanovskii,Struchkov
-
p. 1901 - 1908
(2008/10/08)
-
- Solid-state metathesis as a quick route to transition-metal mixed dichalcogenides
-
Solid-solution transition-metal dichalcogenides, traditionally synthesized from the elements at elevated temperatures over long periods of time, can now be prepared from rapid self-propagating reactions between transition-metal halides and alkali-metal mixed chalcogenides such as Na2(S,Se). The transition-metal dichalcogenide solid solution is isolated by simply washing away the byproduct salt. Powder X-ray diffraction and thermogravimetric analyses of the solid solutions Mo(S,Se)2 and W(S,Se)2 are presented. Although any composition can theoretically be prepared, the stoichiometry of the product is influenced by the temperatures attained during the course of the reaction. The products are characteristically enriched in the more volatile non-metal component relative to the alkali-metal mixed-chalcogenide precursor. The observed kinetic products and selective enrichment suggest that elemental intermediates may be involved in these reactions.
- Bonneau, Philippe R.,Jarvis Jr., Robert F.,Kaner, Richard B.
-
p. 2127 - 2132
(2008/10/08)
-