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# 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 ($$U^{\text{cond}}$$), the total internal mechanical energy ($$U^{\text{mech}}$$), the total chemical energy ($$U^\text{chem}$$) and the harmonic average of the internal temperature ($$\theta_\text{avg}$$) 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:

$\begin{split}U^\text{cond} = & \sum_{i=1}^{N} u_{i}^\text{cond} \\ U^\text{mech} = & \sum_{i=1}^{N} u_{i}^\text{mech} \\ U^\text{chem} = & \sum_{i=1}^{N} u_{i}^\text{chem} \\ U = & \sum_{i=1}^{N} (u_{i}^\text{cond} + u_{i}^\text{mech} + u_{i}^\text{chem}) \\ \theta_{avg} = & \biggl(\frac{1}{N}\sum_{i=1}^{N} \frac{1}{\theta_{i}}\biggr)^{-1} \\\end{split}$

where $$N$$ is the number of particles in the system.

## Output info

This compute calculates a global vector of length 5 ($$U^\text{cond}$$, $$U^\text{mech}$$, $$U^\text{chem}$$, $$\theta_\text{avg}$$, $$N$$), which can be accessed by indices 1 through 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).