compute dpd command¶

Syntax¶

compute ID group-ID dpd

ID, group-ID are documented in compute command
dpd = style name of this compute command

Examples¶

compute 1 all dpd

Description¶

Define a computation that accumulates the total internal conductive energy (\(U^{cond}\)), the total internal mechanical energy (\(U^{mech}\)), the total chemical energy (\(U^{chem}\)) and the harmonic average of the internal temperature (\(\theta_{avg}\)) for the entire system of particles. See the compute dpd/atom command if you want per-particle internal energies and internal temperatures.

The system internal properties are computed according to the following relations:

\[\begin{split}U^{cond} = & \displaystyle\sum_{i=1}^{N} u_{i}^{cond} \\ U^{mech} = & \displaystyle\sum_{i=1}^{N} u_{i}^{mech} \\ U^{chem} = & \displaystyle\sum_{i=1}^{N} u_{i}^{chem} \\ U = & \displaystyle\sum_{i=1}^{N} (u_{i}^{cond} + u_{i}^{mech} + u_{i}^{chem}) \\ \theta_{avg} = & (\frac{1}{N}\displaystyle\sum_{i=1}^{N} \frac{1}{\theta_{i}})^{-1} \\\end{split}\]

where \(N\) is the number of particles in the system

Output info¶

This compute calculates a global vector of length 5 (\(U^{cond}\), \(U^{mech}\), \(U^{chem}\), \(\theta_{avg}\), \(N\)), which can be accessed by indices 1-5. See the Howto output page for an overview of LAMMPS output options.

The vector values will be in energy and temperature units.

Restrictions¶

This command is part of the DPD-REACT package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info.

This command also requires use of the atom_style dpd command.

Default¶

none

(Larentzos) J.P. Larentzos, J.K. Brennan, J.D. Moore, and W.D. Mattson, “LAMMPS Implementation of Constant Energy Dissipative Particle Dynamics (DPD-E)”, ARL-TR-6863, U.S. Army Research Laboratory, Aberdeen Proving Ground, MD (2014).