The x-ray characteristic temperature of potassium bromide as a function of temperature

Abstract The X-ray characteristic temperature Θ M of KBr has been measured in the temperature range of 100–650°K. Using the frequency spectrum of KBr, which has recently been determined both from theoretical calculations and from neutral measurements of the dispersion relations, values of θ M have been calculated over the same temperature range. At low temperatures the computed results are in excellent agreement with the experimental results. At high temperatures the experimental values decrease nearly linearly with temperature in accordance with that predicted by the explicit dependence of Θ M upon the volume. Values of the total root mean square displacement of the ions have been calculated as a function of temperature assuming both ions have the same temperature factor, which is a fair approximation according to recent theoretical calculations. Experimental values of the displacements are found to be in good agreement with theory at low temperatures but show a stronger temperature dependence at high temperatures.