An analytic many-body potential is derived for the bond order of s-valent systems which allows the influence of the local atomic environment on the bond strength to be determined directly. The importance of the three-membered- and four-membered-ring terms on the topology of four-atom clusters is demonstrated. The simplicity of the potential’s analytic form will allow the much used embedded atom potentials to be extended to include explicit three-body and four-body terms.

• Received 18 August 1989

DOI:https://doi.org/10.1103/PhysRevLett.63.2480