Massively parallel dual control volume grand canonical molecular dynamics with LADERA II. Gradient driven diffusion through polymers

Abstract

This paper, the second part of a series, extends the capabilities of the LADERA FORTRAN code for massively parallel dual control volume grand canonical molecular dynamics (DCVGCMD). DCV-GCMD is a hybrid of two more common molecular simulation techniques (grand canonical Monte Carlo and molecular dynamics) which allows the direct molecularlevel modelling of diffusion under a chemical potential gradient. The present version of the code, LADERA-B has the capability of modelling systems with explicit intramolecular interactions such as bonds, angles, and dihedral rotations. The utility of the new code for studying gradient-driven diffusion of small molecules through polymers is demonstrated by applying it to two model systems. LADERA-B includes another new feature, which is the use of neighbour lists in force calculations. This feature increases the speed of the code but presents several challenges in the parallel hybrid algorithm. There is discussion on how these problems were addressed and how our implementation results in a significant increase in speed over the original LADERA. Scaling results are presented for LADERA-B on two massively parallel message-passing machines.