8.7. MC MOVE

The most widely used MC move is the displacement of one monomer at a time (equivalent to particle displacement move in non-polymer system). One MC step is defined as N number of attempted move, where N is the total number of monomer present in the system. In the following sections we will illustrate few MC moves, which are widely used in simulating polymer both in solution and in melt. These moves are principally applicable in the lattice system; however implementation in the off-lattice system is straight forward. We will keep our discussion in the lattice frame work.

8.7.1. Bond fluctuation:

During the moment of a monomer, the bonds associated with that monomer are supposed to vary and may have a different length. As we know a covalent bond is the result of the overlapping of electron cloud. It may fluctuate across a mean value. This fact has been implemented in the MC simulation of polymer, known as bond fluctuation originally developed in 1988 (ref) for the eight site lattice model. Subsequently, it has been modified to the single site lattice model (ref). In this model, a bond is allowed to take up a value from a set of allowable values. In a single site bond fluctuation model, a bond can have 1, √2 (in 2d) and 1, √2, √3 (in 3d) in the lattice frame work. Similarly for off- lattice simulation, bond length is chosen from a pre-defined range so that the fluctuation of the bond length is implemented.