ZN UNDER PRESSURE - A SINGULARITY IN THE HCP STRUCTURE AT C/A=ROOT-3

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-o = 0.893 (P = 9.1 GPa), where the c/a ratio becomes exactly root 3. The anomaly is most likely related to the electronic topological transition recently found with Mossbauer spectroscopy. The special value (root 3) of the axial ratio at the anomaly is, however, difficult to explain simply by the electronic topological transition.