Bond fluctuation model
The bond fluctuation model has been used in the recent past to simulate a great variety of polymer systems (see Ref.s 1 and 2). It represents non-fixed bond lengths and 8-site non-overlapping beads placed in a simple cubic lattice. Bonds linking the beads may have lengths ranging between 2 and , but bonds vectors of the type (2,2,0) are excluded to avoid bond crossing during the simulation.
This model exhibits some advantages with respect to more conventional representations of the polymer in a lattice, such as the fixed-bond self-avoiding walk chain model on a simple cubic lattice:
- It is somehow more consistent with the theoretical description of the chain through Gaussianly distributed statistical segments. This description has been employed in the past to obtain useful analytical expression for equilibrium properties and its dynamical version corresponds to the Rouse model.
- A variety of bond lengths alleviate the restrictions due to the lattice constraints and, therefore, the model is more similar to the continuum behavior.
- It is possible to perform simulations by using a single type of elementary bead jump. This is a difference with respect to the simple cubic lattice model where a combination of bent and crankshaft elementary moves has to be used as the simplest local level. The implication is that one can generate dynamic trajectories with the bond fluctuation model by using a simple and natural type of bead jumps, which intuitively resembles the stochastic behavior of Brownian particles.
- The elementary jump moves can directly used in polymers with branch points (stars, combs, dendrimers).