Nonperiodic stochastic boundary conditions for molecular dynamics simulations of materials embedded into a continuum mechanics domain

Abstract

A scheme is described for performing molecular dynamics simulations on polymers under nonperiodic, stochastic boundary conditions. It has been designed to allow later the embedding of a particle domain treated by molecular dynamics into a continuum environment treated by finite elements. It combines, in the boundary region, harmonically restrained particles to confine the system with dissipative particle dynamics to dissipate energy and to thermostat the simulation. The equilibrium position of the tethered particles, the so-called anchor points, are well suited for transmitting deformations, forces and force derivatives between the particle and continuum domains. In the present work the particle scheme is tested by comparing results for coarse-grained polystyrene melts under nonperiodic and regular periodic boundary conditions. Excellent agreement is found for thermodynamic, structural, and dynamic properties.

Size Effects in a Silica-Polystyrene Nanocomposite: Molecular Dynamics and Surface-enhanced Continuum Approaches

“…In particular, the density of CG silica (2.268 g/cm 3 ) differs from the density of natural quartz [2.649 g/cm 3 (45)]. The bulk density for PS has been obtained as 1.158 g/cm 3 and compares favorably with the findings of a previous CG study (32) in which a density of 1.020 ± 0.00043 g/cm 3 at 300K was reported (Tables 2 and 3).…”

“…We have so-called core beads with full coordination as well as surface beads. Similar to previous studies (1,3,32), each styrene monomer is described by a CG bead where the interaction center is located at the center-of-mass of the monomer. Two different beads (R and S) are required to maintain the information on the chirality of a PS chain.…”

Optimisation of the Capriccio Method to Couple Particle- and Continuum-Based Simulations of Polymers

“…3 Spatial coupling set-up of the Capriccio method with weighting factor : the system consists of continuum c , bridging domain b and particle domain d ; Anchor points serve as auxiliary particles; cf. "Weighting factor" for definition of the MD system under SBCs, the role of anchor points, and physical and computational aspects can be found in one of our preceding articles [15].…”

Scalability of Coarse‐Grained Potentials Generated from Iterative Boltzmann Inversion for Polymers: Case Study on Polycarbonates

“…During the last two decades attempts to develop multiscale models of polymeric systems have been explored. The aim is to access the experimental length and time scales that are normally much larger than those accessible to standard atomistic models . There are numerous reports where scientists try to link the atomistic to mesoscopic scales and then back to the atomistic scale by reverse mapping–or even to merge atoms and coarse‐grained beads in a single model ,.…”