Simulation of Entangled Polymers with Dissipative ... - Lammps

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Background Atomistic K-G Hard atoms t d ~N 3.5 t~N 3*(1/2) x R R g Reptation DPD Hard beads Rouse Soft Beads DN How to prevent chain crossing, and still be fast? …apply force between bonds 2N e Kremer-Grest 10 5 1/s 250,000 beads DPD/SRP 10 5 1/s 40,000 beads Yelena Sliozberg, unpublished
Dissipative Particle Dynamics F F F i C ij D ij ji a F ij C ij F D ij F R ij F SRP ij 1 r ˆ r r ij /rc r ij ij c 0 rij rc D r r ˆ v rˆ ij ij ij ij F H ij F A ij Total Force DPD R R ij F ˆ ij r ij Groot and Warren, J. Δt Chem. Phys. 1997 D 2 F F E SRP ij H ij ijk r R 2k T B r E aij 0 K(r r ) rˆ 2 1 d / ˆ d d ij d c d ij ij c d d 0 K cos( ) ij ij c SRP Segmental Repulsive Potential Goujon et. al, J. Chem. Phys. 129, 034902 (2008) Bond & Angle Current SRP •minimum distance between two bonds •distribute force unevenly between atoms •slow, sometimes overshoots d ij mSRP (new) •midpoint distance between bonds Requires new •distribute force evenly parameters for SRP, •faster, accurate angle potentials Goujon [1] 0F mSRP ½F F ½ F d d ij ij -¾ F -¼ F -½ F -½ F 58 mult/add, 2 div, 2 if 18 mult/add DPD + SRP + Bond + Angles SRP implemented in LAMMPS •communicate ‘ghost bonds’ with forward_pair_comm() •build a bond neighbor list •newton bond off, apply force to local atoms d kl =P k +t k R k ‐P l ‐t l R l d(d kl )/d(R k )=d(d kl )/d(R l )=0 d kl =P k ‐P l 1. J. Chem. Phys. 129, 034902, 2008 2. J. Chem. Phys. 114 (15) p6937, 1997
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