Study of volume and surface plasmons in small silicon-hydrogen nanoclusters by GW method

Numerical calculations of surface and volume plasma excitations in silicon and silicon-hydrogen nanoclusters in the range Si$_{10}$-Si$_{60}$ and Si$_3$H$_8$-Si$_{39}$H$_{40}$ are performed. Some nanocluster structures were obtained using the evolutionary algorithm, others were taken from the database. The GW method was used to calculate the response function and self-energy of the structures under study. The applied method shows the results consistent with the experiment (except plasmaron artifacts) and sufficient sensitivity allowing to investigate the effect of the cluster structure and size on the specific properties of plasma excitations. In the studied silicon and silicon-hydrogen nanoclusters the surface is one of the key factors affecting the properties of the plasmons. Passivation of silicon dangling bonds on cluster surface changes frequency of plasmons and significantly decreases their damping. It makes the surface and volume plasmons to be clearly distinguishable even in small clusters.