A novel parallel-rotation algorithm for atomistic Monte Carlo simulation of dense polymer systems

We develop and test a new elementary Monte Carlo move for use in the off-la ttice simulation of polymer systems. This novel Parallel-Rotation algorithm (ParRot) permits moving very efficiently torsion angles that are deeply in side long chains in melts. The parallel-rotation move is extremely simple a nd is also demonstrated to be computationally efficient and appropriate for Monte Carlo simulation. The ParRot move does not affect the orientation of those parts of the chain outside the moving unit. The move consists of a c oncerted rotation around four adjacent skeletal bonds. No assumption is mad e concerning the backbone geometry other than that bond lengths and bond an gles are held constant during the elementary move. Properly weighted sampli ng techniques are needed for ensuring detailed balance because the new move involves a correlated change in four degrees of freedom along the chain ba ckbone. The ParRot move is supplemented with the classical Metropolis Monte Carlo, the Continuum-Configurational-Bias, and Reptation techniques in an isothermal-isobaric Monte Carlo simulation of melts of short and long chain s. Comparisons are made with the capabilities of other Monte Carlo techniqu es to move the torsion angles in the middle of the chains. We demonstrate t hat ParRot constitutes a highly promising Monte Carlo move for the treatmen t of long polymer chains in the off-lattice simulation of realistic models of dense polymer systems. (C) 2001 American Institute of Physics.