# fix tdpd/source command

## Syntax

fix ID group-ID edpd/source keyword values ...
fix ID group-ID tdpd/source cc_index keyword values ...

• ID, group-ID are documented in fix command

• edpd/source or tdpd/source = style name of this fix command

• index (only specified for tdpd/source) = index of chemical species (1 to Nspecies)

• keyword = sphere or cuboid

sphere values = cx,cy,cz,radius,source
cx,cy,cz = x,y,z center of spherical domain (distance units)
source = heat source or concentration source (flux units, see below)
cuboid values = cx,cy,cz,dLx,dLy,dLz,source
cx,cy,cz = x,y,z lower left corner of a cuboid domain (distance units)
dLx,dLy,dLz = x,y,z side length of a cuboid domain (distance units)
source = heat source or concentration source (flux units, see below)


## Examples

fix 1 all edpd/source sphere 0.0 0.0 0.0 5.0 0.01
fix 1 all edpd/source cuboid 0.0 0.0 0.0 20.0 10.0 10.0 -0.01
fix 1 all tdpd/source 1 sphere 5.0 0.0 0.0 5.0 0.01
fix 1 all tdpd/source 2 cuboid 0.0 0.0 0.0 20.0 10.0 10.0 0.01


## Description

Fix edpd/source adds a heat source as an external heat flux to each atom in a spherical or cuboid domain, where the source is in units of energy/time. Fix tdpd/source adds an external concentration source of the chemical species specified by index as an external concentration flux for each atom in a spherical or cuboid domain, where the source is in units of mole/volume/time.

This command can be used to give an additional heat/concentration source term to atoms in a simulation, such as for a simulation of a heat conduction with a source term (see Fig.12 in (Li2014)) or diffusion with a source term (see Fig.1 in (Li2015)), as an analog of a periodic Poiseuille flow problem.

If the sphere keyword is used, the cx,cy,cz,radius defines a spherical domain to apply the source flux to.

If the cuboid keyword is used, the cx,cy,cz,dLx,dLy,dLz defines a cuboid domain to apply the source flux to.

Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. No global or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

## Restrictions

This fix is part of the USER-MESO package. It is only enabled if LAMMPS was built with that package. See the Build package doc page for more info.

Fix edpd/source must be used with the pair_style edpd command. Fix tdpd/source must be used with the pair_style tdpd command.