The electronic structure of liquid alkali metals: calculation of photoemission spectra

The authors present a first-principles calculation of the atomic structure (pair correlation function, static structure factor), the electronic structure (total and partial densities of states), and of the photoemission intensities of liquid Li and Na. They find that in liquid Li the electronic density of states shows a strong structure-induced 'Brillouin-kink' which leads to a pronounced narrowing of the width of the occupied band compared to the prediction of the free electron model. The DOS of liquid Na on the other hand is close to the free electron parabola. The origin of the difference is in the strong p component in the electron-ion potential in Li, but not in Na. The observed deviation of the photoemission spectrum of Na from a free electron form is explained in terms of the partial photoionisation cross-sections. A detailed comparison with experiment shows that the accuracy of the theoretical predictions is limited only by the local density approximation for the many-electron interactions.