# ATC: fix_modify AtC atom_weight

# fix_modify AtC atom_weight

## syntax

fix_modify AtC atom_weight <method> <arguments>

- <method> =
  value: atoms in specified group assigned constant value given
  lattice: volume per atom for specified lattice type (e.g. fcc) and parameter
  element: element volume divided among atoms within element
  region: volume per atom determined based on the atom count in the MD regions and their volumes. Note: meaningful only if atoms completely fill all the regions.
  group: volume per atom determined based on the atom count in a group and its volume
  read_in: list of values for atoms are read-in from specified file

## examples

`fix_modify atc atom_weight constant myatoms 11.8`
`fix_modify atc atom_weight lattice`
`fix_modify atc atom_weight read-in atm_wt_file.txt`

## description

Command for assigning the value of atomic weights used for atomic integration in atom-continuum coupled simulations.

## restrictions

Use of lattice option requires a lattice type and parameter is already specified.

## related

## default

lattice