fix_modify AtC fields command — LAMMPS documentation

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# fix_modify AtC fields command

## Syntax

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

- AtC fixID = ID of fix atc instance

- fields = name of the AtC sub-command

- all or none = output all or no fields

- add or delete = add or delete the listed output fields

- list_of_fields = one or more of the fields listed below:

  - 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

  - kinetic_temperature : temperature derived from the full kinetic energy

  - number_density : simple kernel estimation of number of atoms per unit volume

  - stress : Cauchy stress tensor for eulerian analysis (atom_element_map), or first Piola-Kirchhoff stress tensor for lagrangian analysis

  - transformed_stress : first 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

  - potential_energy : potential energy per unit volume

  - kinetic_energy : kinetic energy per unit volume

  - thermal_energy : thermal energy (kinetic energy - continuum kinetic energy) per unit volume

  - internal_energy : total internal energy (potential + thermal) per unit volume

  - energy : total energy (potential + kinetic) per unit volume

  - number_density : number of atoms per unit volume

  - eshelby_stress : configurational stress (energy-momentum) tensor defined by [Eshelby]

  - vacancy_concentration : volume fraction of vacancy content

  - type_concentration : volume fraction of a specific atom type

## Examples

    fix_modify AtC fields add velocity temperature

## Description

Allows modification of the fields calculated and output by the AtC transfer class. The commands are cumulative, e.g.:

    fix_modify AtC fields none
    fix_modify AtC fields add velocity temperature

will only output the velocity and temperature fields.

## Restrictions

Must be used with fix atc hardy. 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 AtC commands

- fix_modify AtC command overview

- fix_modify AtC gradients

- fix_modify AtC rates

- fix_modify AtC computes

## Default

By default, no fields are output.

## References

[Eshelby]

J.D. Eshelby, Philos. Trans. Royal Soc. London A, Math. Phys. Sci., Vol. 244, No. 877 (1951) pp. 87-112; J. Elasticity, Vol. 5, Nos. 3-4 (1975) pp. 321-335]