Sodium under pressure: bcc to fcc structural transition and pressure-volume relation to 100 GPa

The pressure-volume relation of sodium is measured up to 100 GPa using high-resolution angle-dispersive synchrotron x-ray diffraction. At a pressure of 65(1) GPa Na is found to undergo a structural phase transition from a body-centered to a face-centered-cubic modification. Total-energy calculations of Na under pressure are performed using the full-potential linearized augmented plane-wave method. The calculated pressure-volume relations and the bcc-fcc transition pressure are compared to the experimental results.