The thermal expansion of rubidium chloride at low temperatures

Measurements of the linear thermal expansion coefficient of rubidium chloride are reported between 30 and 260 K. The results are believed to be accurate to within 1% down to 200 K, falling to 2% at 30 K. The Gruneisen parameter gamma = beta VK T /C v has been shown to fall monotonically from a high temperature limiting value of 1.46. The quasiharmonic approximation has been applied to these and complementary heat capacity and elasticity data to calculate the moments of the vibrational frequency distribution and their volume dependence, interpolation being employed at the lowest temperatures. The results of these calculations conform to the pattern of behaviour which has emerged from earlier comparative studies of sodium and potassium halides.