The adsorption of carbon trimers on Si(1 1 1) 1 x 1 is investigated by means of empirical molecular dynamics based on a Tersoff potential. A priori unknown carbon terminated Si(I 1 1) surfaces are modeled. The energetics of different adsorption sites, specifically the S5, T4 and H3 sites are investigated. The obtained structural models are used to simulate their response to a RHEED experiment. This enables us to further elucidate on the feasibility of the models by comparing theoretical data to in situ RHEED observations during the MBE experiments. Implications of the models to growth of 3C SiC by carbonization are discussed.