The BFM (bond fluctuation model or bond fluctuation method) is a lattice model for simulating the conformation and dynamics of polymer systems.
Each lattice position can only be occupied by one monomer in order to model excluded volume.
The combination of bond vector set and monomer shape in this model ensures that polymer chains cannot cross each other, without explicit test of the local topology.
The basic movement of a monomer cube takes place along the lattice axes so that each of the possible bond vectors can be realized.
However, the lattice points, or vertices of each cube are the sites that can be occupied by a monomer.
Successive monomers along a polymer backbone are connected by bond vectors.
In addition to the bond length constraint, polymers should not be allowed to cross.
In both versions of the BFM, a single attempt to move one monomer consists of the following steps which are standard for Monte Carlo methods: The conditions to perform a move can be subdivided into mandatory and optional ones.
The number of Monte Carlo steps of the total system is defined as: