The use of electron gas modification in the evaluation of the vibration frequencies and the specific heats of sodium and potassium

The earlier work on the determination of the specific heats of lithium by the use of deLaunay’s model has been extended to sodium and potassium. A new technique has been introduced in which the contributions of the central and the outer parts of the Brillouin zone to Cv are calculated separately from different distribution densities of 8000 and 1000 points per zone, respectively. The agreement between the calculated and the experimental values of Cv has been found to be very good except at very low temperatures where the deviations can be ascribed to the presence of phase transformation. The effect of using a finer mesh of points on Cv has been examined. In order to get accurate values of Cv the density of points in the central region has to be increased considerably. In the outer region, however, a low density of eight points per zone as in Raman’s theory is found to be reasonably satisfactory.