Dense orientationally ordered states of a single semiflexible macromolecule:An expanded ensemble Monte Carlo simulation

摘要

Using a coarse-grained model we perform a Monte Carlo simulation of the state behavior of an individual semiflexible macromolecule.Chains consisting of N=256 and 512 monomer units have been investigated.A recently proposed enhanced sampling Monte Carlo technique for the bond fluctuation model in an expanded ensemble in four-dimensional coordinate space was applied.The algorithm allows one to accelerate the sampling of statistically independent three-dimensional conformations in a dense globular state.We found that the temperature of the intraglobular liquid-solid transition decreases with increasing chain stiffness.We have investigated the possible intraglobular orientationally ordered(i.e.,liquid-crystalline)structures and obtained a diagram of states for chains consisting of N-256 monomer units.This diagram contains regions of stability of coil,two spherical globules(liquid and solid),and rod-like globule conformations.Transitions between the globular states are rounded first-order ones since the states of liquid,solid,and cylinder-like globules do have different internal symmetry.