Zn under Pressure: A Singularity in the hcp Structure at c/a= sqrt 3.

Abstract

High-pressure powder x-ray diffraction experiments on Zn at room temperature have revealed that the volume dependence of the $c/a$ axial ratio changes the slope at ${V/V}_{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.893$ ( $P\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}9.1$ GPa), where the $c/a$ ratio becomes exactly $\sqrt{3}$. The anomaly is most likely related to the electronic topological transition recently found with M\"ossbauer spectroscopy. The special value $(\sqrt{3})$ of the axial ratio at the anomaly is, however, difficult to explain simply by the electronic topological transition.