ATOMIC-STRUCTURE AND PHYSICAL-PROPERTIES OF AMORPHOUS-CARBON AND ITS HYDROGENATED ANALOGS

A semiempirical molecular-dynamic density-functional approach is used to perform a systematic investigation of the stability, structure, and properties of quenched pure and hydrogenated amorphous carbon depende nt on the mass density and the hydrogen concentration. By comparing th e total structure energies for supercell clusters of equal composition and atom number, we obtain the most stable a-C:H configurations chara cterized by optimal chemical bonding corresponding to certain mass den sities and hydrogen concentrations which control the short- and medium -range order in the material. We present a detailed structural analysi s of stable and metastable a-C:H modifications comparing theoretically simulated diffraction data with electron-scattering results. In addit ion, we discuss correlations between the atomic structure and the elec tronic properties which in turn are mediated by the chemical bonding a nd the clustering of different hybridized atoms.