Effect of Temperature and Pressure on the Resistance of Four Alkali Metals

Abstract

The electrical resistance of lithium, sodium, potassium, and rubidium has been measured as a function of pressure to over 500 kbar at 77\ifmmode^\circ\else\textdegree\fi{}K and 296\ifmmode^\circ\else\textdegree\fi{}K. Lithium exhibits an initial rise in resistance, a first-order phase transition at 70 kbar with a large resistance crop, and a very gradual rise in resistance at high pressure. Sodium has a rise in resistance with pressure at both 77 and 296\ifmmode^\circ\else\textdegree\fi{}K. The high-temperature isotherm exhibits a very broad maximum at high pressure. For potassium, the 296\ifmmode^\circ\else\textdegree\fi{}K isotherm shows a rise by a factor of 50 in 600 kbar. The 77\ifmmode^\circ\else\textdegree\fi{}K isotherm shows a sluggish transition at 280 kbar and a very sharp transition at 360 kbar. The latter is almost certainly martensitic. Both isotherms for rubidium have qualitatively similar behavior: a rise in resistance which accelerates with increasing pressure, a discontinuous rise at 190 kbar (210 kbar at 77\ifmmode^\circ\else\textdegree\fi{}K), and a broad maximum at high pressure. The discontinuous rise is probably due to a electronic transition.