Pressure induced phase transition in Fe0.47NbS2 studied by powder X-ray diffraction

The structural behavior of Fe0.47 NbS2 at high pressure has been investigated by angular dispersive synchrotron powder diffraction up to 13.63(7) GPa. A first-order phase transition was observed between 6.92(4) and 7.49(4) GPa. It is an isostructural transition that is accompanied by a volume discontinuity of about 4% at the transition. The compression behavior of the structure is highly anisotropic. The compressibility perpendicular to the layers is significantly higher than within the layers. The bulk moduli, derived from fits of second-order Birch–Murnaghan equations of state, are B0=87(1)B0=87(1)  GPa for the low-pressure phase Fe0.47 NbS2-I and B0=112(1)B0=112(1)  GPa for the high-pressure phase Fe0.47 NbS2-II, respectively. A change in the electronic or spin state of the iron in the van der Waals gap is assumed to govern the observed phase transi- tion.