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".

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