Tantalum(IV) sulfide

Tantalum(IV) sulfide

Names
Other names tantalum disulfide
Identifiers
CAS Number	12143-72-5 Y
Jmol 3D model	Interactive image
PubChem	82945
InChI InChI=1S/2S.Ta
SMILES S=[Ta]=S
Properties
Chemical formula	TaS2
Molar mass	245.08 g/mol
Appearance	black crystals
Density	6.86 g/cm3, solid
Melting point	3,000 °C (5,430 °F; 3,270 K)
Structure
Crystal structure	hexagonal
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Tantalum(IV) sulfide is the inorganic compound with the formula TaS₂. It is a layered compound with three-coordinate sulfide centres and trigonal prismatic metal centres. It is structurally similar to the more famous material molybdenum disulfide, MoS₂. TaS₂ is a semiconductor with d¹ electron configuration. Although an obscure material otherwise, TaS₂ has been the subject of many studies because it is a versatile host for intercalation of electron donors.

Preparation

TaS₂ is prepared by the high temperature reaction of powdered tantalum and sulfur. It is purified and crystallized by chemical vapor transport using iodine as the transporting agent:

TaS₂ + 2 I₂ $\overrightarrow{\leftarrow}$ TaI₄ + 2 S

Crystallographic structure

The crystallographic structure of tantalum disulfide shows a number of complexities. One of its forms 1T-TaS₂ undergoes a number of phase transitions as a function of temperature. In the lowest temperature phase, the commensurate phase (below 180K) there is a commensurate superstructure, known as a charge density wave (CDW), at an angle of 13.9 degrees relative to the lattice. In an incommensurate phase above 353K the wave is aligned with the lattice. Two more structures exist: a nearly commensurate one appears between 353K and 180K upon cooling. Upon warming a triclinic phase is first formed between 223K and 283K to revert to the nearly commensurate one at 283K. Both these phases have different superstructures.