# fix_modify AtC transfer fields

## syntax

fix_modify AtC transfer fields <all | none>
fix_modify AtC transfer fields <add | delete> <list_of_fields>

- all | none (keyword) = output all or no fields
- add | delete (keyword) = add or delete the listed output fields
- fields (keyword) =
  density : mass per unit volume
  displacement : displacement vector
  momentum : momentum per unit volume
  velocity : defined by momentum divided by density
  projected_velocity : simple kernel estimation of atomic velocities
  temperature : temperature derived from the relative atomic kinetic energy (as done by Hardy)
  kinetic_temperature : temperature derived from the full kinetic energy
  energy : total energy (potential + kinetic) per unit volume
  number_density : simple kernel estimation of number of atoms per unit volume
  stress : Cauchy stress tensor for eulerian analysis (atom_element_map), or 1st Piola-Kirchhoff stress tensor for lagrangian analysis
  transformed_stress : 1st Piola-Kirchhoff stress tensor for eulerian analysis (atom_element_map), or Cauchy stress tensor for lagrangian analysis
  heat_flux : spatial heat flux vector for eulerian, or referential heat flux vector for lagrangian

## examples

`fix_modify AtC transfer fields add velocity temperature`

## description

Allows modification of the fields calculated and output by the Hardy transfer class. The commands are cumulative, e.g.
`fix_modify AtC transfer fields none`
followed by
`fix_modify AtC transfer fields add velocity temperature`
will only output the velocity and temperature fields.

## restrictions

Must be used with the hardy AtC transfer, see fix atc command. Currently, the stress and heat flux formulas are only correct for central force potentials, e.g. Lennard-Jones and EAM but not Stillinger-Weber.

## related

See fix_modify AtC transfer gradients , fix_modify AtC transfer rates and fix_modify AtC transfer computes

## default

All fields are output by default