Linear response approach to collective electronic excitations of solids and surfaces

We have developed a parallel computer-program for the study of dynamic response of periodic Systems. It Computes the linear response of in interacting many-electron system from its ground-state electronic structures, which are obtained from ob initio band structure calculations ill the plane-wave and pseudopotential scheme. As test examples, we applied this program to calculate the linear response of bulk aluminum and a beryllium monolayer, The excitation spectra show prominent plasmon resonances, which compare well with the available data and previous calculations. For surfaces or thin films, we found that removing periodicity perpendicular to the Surface gives a more reliable description of the low-energy excitation spectra, especially in the long-wavelength limit.