The 63 K phase transition of ZrTe3: a neutron diffraction study

The 63 K phase transition of ZrTe3, has been followed through SQUID magneti sation and neutron diffraction studies. The transition is characterized by a small quenching of the magnetic susceptibility. Contrary to the expectati on that the structural transition is associated with a charge density wave, the results of Rietveld refinements of high resolution neutron powder diff raction profiles indicate that below the phase transition the different bon ding Te-Te contacts are more equal rather than less. The results are examin ed with the help of band, structure calculations on structures determined a t three different temperatures. The picture that emerges supports the view that anion-cation redox competition plays a crucial role in determining not only the structures of these compounds, but also the temperature dependenc e thereof.