compute pe command — LIGGGHTS v3.X documentation

# compute pe command

## Syntax

    compute ID group-ID pe general_keyword general_values keyword ...

- ID, group-ID are documented in compute command
- pe = style name of this compute command
- general_keywords general_values are documented in compute
- zero or more keywords may be appended
- keyword = pair or bond or angle or dihedral or improper or kspace

## Examples

    compute 1 all pe
    compute molPE all pe bond angle dihedral improper

## Description

Define a computation that calculates the potential energy of the entire system of atoms. The specified group must be “all”. See the compute pe/atom command if you want per-atom energies. These per-atom values could be summed for a group of atoms via the compute reduce command.

The energy is calculated by the various pair, bond, etc potentials defined for the simulation. If no extra keywords are listed, then the potential energy is the sum of pair, bond, angle, dihedral, improper, and kspace (long-range) energy. If any extra keywords are listed, then only those components are summed to compute the potential energy.

Various fixes can contribute to the total potential energy of the system. See the doc pages for individual fixes for details. The thermo option of the compute_modify command determines whether these contributions are added into the computed potential energy. If no keywords are specified the default is yes. If any keywords are specified, the default is no.

Output info:

This compute calculates a global scalar (the potential energy). This value can be used by any command that uses a global scalar value from a compute as input. See Section_howto 15 for an overview of LIGGGHTS(R)-PUBLIC output options.

The scalar value calculated by this compute is “extensive”. The scalar value will be in energy units.

## Restrictions

This compute does not include the potential energy due to the overlap of granular particles.

## Related commands

compute pe/atom

Default: none