Syntax:
pair_style dpd T cutoff seed
Examples:
pair_style dpd 1.0 2.5 34387 pair_coeff * * 3.0 1.0 pair_coeff 1 1 3.0 1.0 1.0
Description:
Style dpd computes a force field for dissipative particle dynamics (DPD) following the exposition in (Groot). The force on atom I due to atom J is given as a sum of 3 terms
where FC is a conservative force, FD is a dissipative force, and FR is a random force. Rij is a unit vector in the direction Ri - Rj, Vij is the vector difference in velocities of the two atoms = Vi - Vj, alpha is a Gaussian random number with zero mean and unit variance, dt is the timestep size, and w(r) is a weighting factor that varies between 0 and 1. Rc is the cutoff. Sigma is set equal to sqrt(2 T gamma), where T is a parameter in the pair_style command.
The following coefficients must be defined for each pair of atoms types via the pair_coeff command as in the examples above, or in the data file or restart files read by the read_data or read_restart commands:
The last coefficient is optional. If not specified, the global DPD cutoff is used. Note that sigma is set equal to sqrt(2 T gamma), where T is the temperature set by the pair_style command so it does not need to be specified.
Restrictions: none
This style is part of the "dpd" package. It is only enabled if LAMMPS was built with those package. See the Making LAMMPS section for more info.
The dpd potential does not support the pair_modify mix option. Coefficients for all i,j pairs must be specified explicitly.
Related commands:
Default: none
(Groot) Groot and Warren, J Chem Phys, 107, 4423-35 (1997).