# fix_modify AtC mesh create_faceset box command

## Syntax

    fix_modify <AtC fixID> mesh create_faceset <id> box <xmin> <xmax> <ymin> <ymax> <zmin> <zmax> <in|out> [units]

-   AtC fixID = ID of [fix atc](fix_atc) instance
-   mesh create_faceset = name of the AtC sub-command
-   id = id to assign to the collection of FE faces
-   box = use bounding box to define FE faces
-   \<xmin\> \<xmax\> \<ymin\> \<ymax\> \<zmin\> \<zmax\> = coordinates
    of the bounding box that is coincident with the desired FE faces
-   \<in\|out\> = \"in\" gives inner faces to the box, \"out\" gives the
    outer faces to the box
-   units = option to specify real as opposed to lattice units

## Examples

``` LAMMPS
fix_modify AtC mesh create_faceset obndy box -4.0 4.0 -12 12 -12 12 out
```

## Description

Command to assign an id to a set of FE faces.

## Restrictions

Only viable for rectangular grids.

## Related AtC commands

-   [fix_modify AtC command overview](atc_fix_modify)
-   [fix_modify AtC mesh create_faceset
    plane](atc_mesh_create_faceset_plane)

## Default

The default options are units = lattice and the use of outer faces.