A spin-polarized first-principles calculation of the atomic and electronic structure of the graphene/Ni(111) interface is presented. Different structural models have been considered, which differ in the positions of the carbon atoms with respect to the nickel topmost layer. The most probable structure, which has the lowest energy, has been determined. The distance between the floating carbon layer and the nickel surface is found smaller than the distance between graphene sheets in bulk graphite, in accordance with experimental measurements. The electronic structure of the graphene layer is strongly modified by interaction with the substrate and the magnetic moment of the surface nickel atoms is lowered in the presence of the graphene layer. Several interface states have been identified in different parts of the interface two-dimensional Brillouin zone. Their influence on the electron energy loss spectra has been evaluated.

The local-field correction for the two-dimensional and the three-dimensional electron gas is calculated within a sum-rule version of the self-consistent approach of Singwi, Tosi, Land, and Sjolander. Correlation effects are studied. Results for 0.001 & r, & 100 are given where r, is the random-phaseapproximation parameter. An analytical expression for the static structure factor, representing a generalized Feynman-Bijl spectrum, is used in the calculation. We derive analytical expressions for the density dependence of the local-field correction and we compare the results for the ground-state energy for the interacting electron gas with Monte Carlo computations. The pair-correlation function and the compressibility are studied. Exchange and correlation effects for quantum wells and heterostructures are calculated: numerical and analytical results are derived. In two dimensions and at low density a roton structure in the plasmon dispersion is found. We discuss an instability in layered structures of twodimensional electron gases.

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