We explore in detail the transferability of classical bulk-derived potentials to microclusters, in the case of silicon. We present a critical comparison of the results of our computer simulations performed both with the local-density-functional (LDF) Car-Parrinello method and with published potentials obtained from fitting to LDF calculations of bulk properties. We show quantitatively that classical potentials give only a poor description of the potential-energy surface of the microclusters. For the latter we provide much of the information needed to construct an improved classical scheme. © 1990 The American Physical Society.