A new approach in each step of which the interfullerene distance is fixed and other degrees of freedom are allowed to relax is proposed to simulate the thermal-driven depolymerization process of a two-dimensional hexagonal C-60 polymer. The resulting depolymerization energy barrier is significantly improved compared with the previous approach in each step of which the lattice constant is fixed while the atomic positions are relaxed. (C) 2004 Elsevier B.V. All rights reserved.