# fix_modify AtC boundary type command

## Syntax

    fix_modify <AtC fixID> boundary type <atom-type-id>

-   AtC fixID = ID of [fix atc](fix_atc) instance
-   boundary type = name of the AtC sub-command
-   atom-type-id = type id for atoms that represent a fictitious
    boundary internal to the FE mesh

## Examples

``` LAMMPS
fix_modify AtC boundary type ghost_atoms
```

## Description

Command to define the atoms that represent the fictitious boundary
internal to the FE mesh. For fully overlapped MD/FE domains with
periodic boundary conditions no boundary atoms should be defined.

## Restrictions

None.

## Related AtC commands

-   [fix_modify AtC command overview](atc_fix_modify)

## Default

None.