Identifying the bonding in diamond and silicon using compton scattering experiments

Abstract

Theoretical and experimental Compton profiles of diamond and silicon are analysed in terms of the reconstructed electron momentum density, ρ( p), and its Fourier transform, B( r). The bonding molecular orbitals in the tetrahedral structure and the longer range interaction between neighbouring bonds are both sources of anisotropy in ρ( p) and B( r). The relative importance of these electronic interactions in diamond and silicon is discussed in terms of localized models of the electron distribution, with particular emphasis on the Wannier function representation. Available theoretical descriptions of the electronic structure in diamond lattices indicate that it is the first parallel bond neighbour which introduces the most serious modification into the idealized sp 3 bond model. This interaction can be identified in the present experimental results and in the earlier measurements performed in Bell Laboratories. The Fourier transform of the electron momentum density has proved to be a useful representation for identifying the bond information contained in Compton data.