The use of Frozen Core Orbitals (FCOs) at the frontier atom is proposed as an alternative to the specific frontier bond potential in the Local-SCF/MM method. The calculations illustrate that frontier bond length is correctly recovered without adding any specific forcefield potential. It is shown that the same accuracy is reached for calculations using FCOs arising either from an atomic (ROHF) or from a molecular calculation using Extremely Localized Molecular Orbitals (ELMOs). In addition FCOs do not modify the description of the remaining of the QM subsystem from both an energetic and/or geometric point of view. (c) 2006 Elsevier B.V. All rights reserved.