git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@14950 f3b2605a-c512-4ea7-a41b-209d697bcdaa

doc/html/_sources/fix_evaporate.txt

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+.. index:: fix evaporate
+
+fix evaporate command
+=====================
+
+Syntax
+""""""
+
+.. parsed-literal::
+
+   fix ID group-ID evaporate N M region-ID seed
+
+* ID, group-ID are documented in :doc:`fix <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
+* zero or more keyword/value pairs may be appended
+.. parsed-literal::
+
+   keyword = *molecule*
+     *molecule* value = *no* or *yes*
+
+
+
+Examples
+""""""""
+
+.. parsed-literal::
+
+   fix 1 solvent evaporate 1000 10 surface 49892
+   fix 1 solvent evaporate 1000 10 surface 38277 molecule yes
+
+Description
+"""""""""""
+
+Remove M atoms from the simulation every N steps.  This can be used,
+for example, to model evaporation of solvent particles or moleclues
+(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.
+
+If the setting for the *molecule* keyword is *no*\ , then only single
+atoms are deleted.  In this case, you should insure you do not delete
+only a portion of a molecule (only some of its atoms), or LAMMPS will
+soon generate an error when it tries to find those atoms.  LAMMPS will
+warn you if any of the atoms eligible for deletion have a non-zero
+molecule ID, but does not check for this at the time of deletion.
+
+If the setting for the *molecule* keyword is *yes*\ , then when an atom
+is chosen for deletion, the entire molecule it is part of is deleted.
+The count of deleted atoms is incremented by the number of atoms in
+the molecule, which may make it exceed *M*\ .  If the molecule ID of the
+chosen atom is 0, then it is assumed to not be part of a molecule, and
+just the single atom is deleted.
+
+As an example, if you wish to delete 10 water molecules every *N*
+steps, you should set *M* to 30.  If only the water's oxygen atoms
+were in the fix group, then two hydrogen atoms would be deleted when
+an oxygen atom is selected for deletion, whether the hydrogens are
+inside the evaporation region or not.
+
+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.
+
+.. note::
+
+   If you are monitoring the temperature of a system where the atom
+   count is changing due to evaporation, you typically should use the
+   :doc:`compute_modify dynamic yes <compute_modify>` command for the
+   temperature compute you are using.
+
+Restart, fix_modify, output, run start/stop, minimize info
+""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
+
+No information about this fix is written to :doc:`binary restart files <restart>`.  None of the :doc:`fix_modify <fix_modify>` options
+are relevant to this fix.
+
+This fix computes a global scalar, which can be accessed by various
+:ref:`output commands <howto_15>`.  The scalar is the
+cummulative number of deleted atoms.  The scalar value calculated by
+this fix is "intensive".
+
+No parameter of this fix can be used with the *start/stop* keywords of
+the :doc:`run <run>` command.  This fix is not invoked during :doc:`energy minimization <minimize>`.
+
+Restrictions
+""""""""""""
+
+
+This fix is part of the MISC package.  It is only enabled if LAMMPS
+was built with that package.  See the :ref:`Making LAMMPS <start_3>` section for more info.
+
+Related commands
+""""""""""""""""
+
+:doc:`fix deposit <fix_deposit>`
+
+Default
+"""""""
+
+The option defaults are molecule = no.
+
+
+.. _lws: http://lammps.sandia.gov
+.. _ld: Manual.html
+.. _lc: Section_commands.html#comm