Effect of Pressure on the Volume and Lattice Parameters of Magnesium

Abstract

The effect of pressure to 300 kbar has been measured on the volume and on the lattice parameters ($c$ and $a$) of the hcp magnesium lattice. The $a$ axis compresses in a regular manner, but the $c$ axis compresses relatively rapidly to 70 kbar, then becomes continuously more incompressible in the range 70-120 kbars, which results in a distinct increase in $\frac{c}{a}$. The compressibility increases in the region 120-200 kbar and $\frac{c}{a}$ is essentially constant. Beyond 200 kbar the $c$-axis compressibility decreases again and $\frac{c}{a}$ increases rapidly. These results and earlier measurements of resistance as a function of pressure are interpreted qualitatively in terms of the theories of Jones and Goodenough and the Fermi surface as calculated by Falicov.