On the existence of a critical point for the phase transition in cerium

Abstract

A piston-displacement technique has been used to examine the phase transition in cerium to 20,000 atm and 575°K. The results are in agreement with previous thermal data, and show that the volume change decreases with increasing temperature, extrapolating to zero somewhere near 630°K and 20,000 atm. Above roughly 500°K and 15,000 atm, however, the transition becomes increasingly spread out in pressure at constant temperature, and it becomes quite difficult to assign values to the transition pressures, and the volume changes. Although there are definite indications that the nature of the transition is changing at these pressures and temperatures, the possibility that the transition is merely becoming sluggish cannot be ruled out.