The fusion curves of the alkali metals up to 50 kilobars

Abstract

The fusion curves of Li, Na, K, Rb, and Cs have been determined to pressures of 50 kb. The normal melting points, steepness of initial slopes, and curvatures combine in complicated ways to give many intersections of these fusion curves. A double maximum in the curve of Cs was found, with Cs III, or ‘collapsed’ Cs, having a positive melting slope. No maximum was found in the curve of Rb to 50 kb, although the flatness of this curve at 50 kb suggests an imminent maximum The eutectic melting point in the system Na-K was traced to 30 kb, where it became indiscernible. The pressure effect on this melting point is much lower than that on either Na or K. This may be a general effect for eutectic mixtures and may have some geophysical significance.