Theoretical study of self-diffusion of liquid alkali elements

A new approach to study the variation of the self-diffusion coefficient through the temperature dependence of the topological-short-range-order (TSRO) existing in the liquid phase has been presented. A relation has been obtained for the temperature dependence of the coefficient of self-diffusion (D). Present study indicates that, both the decrease in TSRO as well as the increase in thermal energy govern the trend of self-diffusion coefficient with temperature. Calculated values of the self-diffusion coefficient for alkali elements (Li, Na, K, Rb) are in good agreement with the available experimental data, over a wide range of temperatures (T-m-T-b) i.e. from melting to normal boiling temperature, the maximum deviation is 6.9%. It is found that, the trends of reduced self-diffusion coefficient D-t=D/D-m. versus reduced temperature T-r=T/T-m correspond quite closely, for all alkali elements except lithium, the maximum deviation from common trend being similar to6%.