A Numerical Technique for Preserving the Topology of Polymer Knots: The Case of Short-range Attractive Interactions

The statistical mechanics of single polymer knots is studied using Monte Carlo simulations. The polymers are considered on a cubic lattice and their conformations are randomly changed with the help of pivot transformations. After each transformation, it is checked if the topology of the knot is preserved by means of a method called pivot algorithm and excluded area (in short PAEA) and described in a previous publication of the authors. As an application of this method the specific energy, the radius of gyration and heat capacity of a few types of knots are computed. The case of attractive short-range forces is investigated. The sampling of the energy states is performed by means of the Wang-Landau algorithm. The obtained results show that the specific energy and heat capacity increase with increasing knot complexity as in the case of repulsive interactions. The data about the gyration radius allow to estimate the size of the polymer knots at different temperatures.