The crystal structure of NbSe2 at 15°K

Abstract At 40°K the 2H polytype of NbSe2 undergoes a transition which is accompanied by anomalies in the electrical resistivity and Hall effect. However, our magnetic susceptibility measurements do not show a pronounced anomaly at the transition. The crystal structure of 2HNbSe2 has a layered hexagonal structure with the niobium atoms at the center of trigonal selenium prisms. At the transition the unit cell doubles along the a axis. The hexagonal symmetry is conserved and 2 3 of the niobium atoms are displaced from their 6 m2- point symmetry. The coupling of these niobium atoms seems to be the driving mechanism for the crystallographic distortion.