Dissipative Particle Dynamics at Isoenthalpic Conditions Using Shardlow-Like Splitting Algorithms

Report No. ARL-TR-6587
Authors: John K. Brennan; Martin Lísal
Date/Pages: September 2013; 50 pages
Abstract: A numerical integration scheme based upon the Shardlow-splitting algorithm (SSA) is presented for a Dissipative Particle Dynamics (DPD) approach at fixed pressure and enthalpy. A constant-enthalpy DPD method (DPD-H) is developed by combining the equations of motion (EOM) for a barostat with the EOM for the constant-energy DPD method (DPD-E). The DPD-H variant is developed for both a deterministic (Hoover) and stochastic (Langevin) barostat, where a barostat temperature is defined to satisfy the fluctuation-dissipation theorem for the Langevin barostat. The application of the Shardlow-splitting algorithm is particularly critical for the DPD-H variant because it allows more temporally practical simulations to be carried out. The DPD-H variant using the SSA is verified using both a standard DPD fluid model and a coarse-grain solid model. For both models, the DPD-H variant is further verified by instantaneously heating a slab of particles in the simulation cell and subsequently monitoring the evolution of the corresponding thermodynamic variables as the system approaches an equilibrated state while maintaining constant-enthalpy conditions. The Fokker-Planck equation and derivation of the fluctuation-dissipation theorem are included.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2013