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

doc/html/_sources/pair_write.txt

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+.. index:: pair_write
+
+pair_write command
+==================
+
+Syntax
+""""""
+
+.. parsed-literal::
+
+   pair_write itype jtype N style inner outer file keyword Qi Qj
+
+* itype,jtype = 2 atom types
+* N = # of values
+* style = *r* or *rsq* or *bitmap*
+* inner,outer = inner and outer cutoff (distance units)
+* file = name of file to write values to
+* keyword = section name in file for this set of tabulated values
+* Qi,Qj = 2 atom charges (charge units) (optional)
+
+Examples
+""""""""
+
+.. parsed-literal::
+
+   pair_write 1 3 500 r 1.0 10.0 table.txt LJ
+   pair_write 1 1 1000 rsq 2.0 8.0 table.txt Yukawa_1_1 -0.5 0.5
+
+Description
+"""""""""""
+
+Write energy and force values to a file as a function of distance for
+the currently defined pair potential.  This is useful for plotting the
+potential function or otherwise debugging its values.  If the file
+already exists, the table of values is appended to the end of the file
+to allow multiple tables of energy and force to be included in one
+file.
+
+The energy and force values are computed at distances from inner to
+outer for 2 interacting atoms of type itype and jtype, using the
+appropriate :doc:`pair_coeff <pair_coeff>` coefficients.  If the style
+is *r*\ , then N distances are used, evenly spaced in r; if the style is
+*rsq*\ , N distances are used, evenly spaced in r^2.
+
+For example, for N = 7, style = *r*\ , inner = 1.0, and outer = 4.0,
+values are computed at r = 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0.
+
+If the style is *bitmap*\ , then 2^N values are written to the file in a
+format and order consistent with how they are read in by the
+:doc:`pair_coeff <pair_coeff>` command for pair style *table*\ .  For
+reasonable accuracy in a bitmapped table, choose N >= 12, an *inner*
+value that is smaller than the distance of closest approach of 2
+atoms, and an *outer* value <= cutoff of the potential.
+
+If the pair potential is computed between charged atoms, the charges
+of the pair of interacting atoms can optionally be specified.  If not
+specified, values of Qi = Qj = 1.0 are used.
+
+The file is written in the format used as input for the
+:doc:`pair_style <pair_style>` *table* option with *keyword* as the
+section name.  Each line written to the file lists an index number
+(1-N), a distance (in distance units), an energy (in energy units),
+and a force (in force units).
+
+Restrictions
+""""""""""""
+
+
+All force field coefficients for pair and other kinds of interactions
+must be set before this command can be invoked.
+
+Due to how the pairwise force is computed, an inner value > 0.0 must
+be specified even if the potential has a finite value at r = 0.0.
+
+For EAM potentials, the pair_write command only tabulates the
+pairwise portion of the potential, not the embedding portion.
+
+Related commands
+""""""""""""""""
+
+:doc:`pair_style table <pair_table>`,
+:doc:`pair_style <pair_style>`, :doc:`pair_coeff <pair_coeff>`
+
+**Default:** none
+
+
+.. _lws: http://lammps.sandia.gov
+.. _ld: Manual.html
+.. _lc: Section_commands.html#comm