LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Commands

### fix evaporate command

Syntax:

    fix ID group-ID evaporate N M region-ID seed

- ID, group-ID are documented in fix command
- evaporate = style name of this fix command
- N = delete atoms every this many timesteps
- M = number of atoms to delete each time
- region-ID = ID of region within which to perform deletions
- seed = random number seed to use for choosing atoms to delete

Examples:

    fix 1 solvent evaporate 1000 10 surface 49892

Description:

Remove M atoms from the simulation every N steps. This can be used, for example, to model evaporation of solvent particles (i.e. drying) of a system. Every N steps, the number of atoms in the fix group and within the specifed region are counted. M of these are chosen at random and deleted. If there are less than M eligible particles, then all of them are deleted.

Note that you cannot currently delete solvent molecules with this command, only individual atoms. If you delete only one atom in a molecule, an error will result.

Note that neighbor lists are re-built on timesteps that atoms are removed. Thus you should not remove atoms too frequently or you will incur overhead due to the cost of building neighbor lists.

Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix.

The cummulative number of deleted atoms is stored as a scalar quantity by this fix. This quantity can be accessed by various output commands. The scalar value is "intensive", meaning it is independent of the number of atoms in the simulation.

No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions: none

Related commands:

fix deposit

Default: none