Reversible Iodine Intercalation into Tungsten Ditelluride

The new compound WTe2I was prepared by a reaction of WTe2 with iodine in a fused silica vessel 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 and therefore the c-axis length is significantly increased, and the orthorhombic space group is preserved. Iodine atoms form planar layers between each tungsten ditelluride layer. Due to oxidation by iodine the semi-metallic 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 suggests a charge density wave instability at low temperature.