Dissipative Particle Dynamics at Isoenthalpic Conditions Using Shardlow-Like Splitting Algorithms
Final rept. Feb 2012-Apr 2013
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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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.
- Numerical Mathematics