c/a anomalies and electronic topological transitions in Cd

The total-energy calculations are carried out to obtain the axial ratio (c/a) variation with compression for cadmium. We find two anomalies as compared to a single anomaly at V/V-0 = 0.85 observed in the experimental data. The first anomaly at V/V-0 = 0.95 is due to electronic topological transition (ETT) and correlates well with die anomaly observed in the existing resistivity data. We find the 4d-orbital overlap, coupled with transfer of electrons from d to s states as the cause of second anomaly. This observation is in contrast to the existing understanding in zinc, where the c/a anomaly is attributed to the destruction of a giant Kohn anomaly by ETT. Nondestruction of giant Kohn anomaly in cadmium at high pressures is in disagreement with the current view in the literature that its Fermi surface is identical to that of zinc.