Studies of the kinetics of [NaCl]–[CsCl] transitions

Abstract

Studies were made to determine the effects of various interacting factors (pressure, temperature, mineralizers, and shear) on the kinetics of [NaCl]–[CsCl] transition. These experiments were performed to more fully understand how particular experimental parameters change the kinetics and hence the apparent equilibrium of some solid-state reactions. Results show that the kinetic effects of pressure are so great in some cases that solid-state transformations cannot be greatly ``superpressurized'' by shock-wave techniques. It is recommended that materials which show this effect be used for calibrating shock-wave apparatus. Previously reported kinetic effects of temperature on the [NaCl]–[CsCl] transition for RbCl are shown to be in error. Thus, increasing temperature accelerates reaction rate and reduces the hysteresis for this particular phase transition. Also, with the addition of water as a mineralizer the ``region of indifference'' was found to be equal to the width of the hysteresis loop. The kinetic effect of the crystallographic orientation of single crystals of RbCl and CdS was found to be of such magnitude that orientation should be considered when examining results of any single-crystal phase transition studies. Many widely different experimental results on equilibrium phase boundaries can be sufficiently interpreted when details of experiments revealing unsuspected kinetic problems are known.