Pseudopotential Calculation of Knight-Shift Temperature and Volume Dependence in Liquid and Solid Sodium

We have used a pseudopotential formalism to compute the electron density at a nuclear site in liquid and bcc solid sodium. The temperature dependence of the electron density at atmospheric pressure is found to account satisfactorily for the experimental observation that the sodium Knight shift increases with temperature. A decrease would be expected to accompany lattice expansion in a free-electron metal. In addition, the temperature dependence at constant volume and the pressure dependence of the electron density are computed and compared with published experimental data. Agreement between theory and experiment is rather better for the liquid state than for the solid, probably because of a less than satisfactory approximation to the high-temperature solid lattice structure.