# fix_modify AtC output boundary_integral command

## Syntax

    fix_modify <AtC fixID> output boundary_integral <fieldname> faceset [name]

-   AtC fixID = ID of [fix atc](fix_atc) instance
-   output boundary_integral = name of the AtC sub-command
-   fieldname = name of hardy field
-   faceset = required keyword
-   name= name of faceset

## Examples

``` LAMMPS
fix_modify AtC output boundary_integral stress faceset loop1
```

## Description

Calculates a surface integral of the given field dotted with the outward
normal of the faces and puts output in the \"GLOBALS\" file.

## Restrictions

Must be used with the hardy/field type of [fix atc](fix_atc)

## Related AtC commands

-   [fix_modify AtC command overview](atc_fix_modify)

## Default

None.