# 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).