pair_style dpd

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2.2.15.3 pair_style dpd

Setup the dissipative particle dynamics (DPD) pair style.

pair_style dpd temp r_gcut random-seed
pair_coeff i-type j-type a γ r_cut

temp: target temperature
r_gcut: global cut-off
random-seed: seed for generating random number
a, γ, r_cut: DPD force parameters

Examples:

pair_style dpd 1.0 1.0 22717 2
pair_coeff * * 18.75 4.5 1.0

Description:

The force in the DPD potential have three components: conservative force, dissipative force and random force:

f^I = ∑ _J≠I(f_C^IJ + f_D^IJ + f_R^IJ).

The formulation of these three force components are given below:

f_C^IJ	= a^IJω_Cn^IJ
f_D^IJ	= -γω_D(n^IJ ⋅v^IJ)n^IJ
f_R^IJ	= σω_Rζ^IJ(△t)^-1∕2n^IJ

where ω_D = (ω_R)² =, σ = √ ------
2kBT γ

, and r_cut is the local cutoff set by the command pair_coeff. ζ^IJ is the random number and the “random-seed” is used to generate random number. In DPD, the random number is generated with a Gaussian distribution.

A common choice for the weight functions are given as

ω_C =

(
|{ rIJ- IJ
1- rcut (r < rcut),
|( 0 (rIJ ≥ rcut),

ω_D(r^IJ) = [ω_R(r^IJ)]² =

(( )
|{ rIJ 2 IJ
1- rcut (r < rcut),
|(0 (rIJ ≥ r ),
cut

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