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

doc/html/_sources/compute_pair.txt

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+.. index:: compute pair
+
+compute pair command
+====================
+
+Syntax
+""""""
+
+.. parsed-literal::
+
+   compute ID group-ID pair pstyle evalue
+
+* ID, group-ID are documented in :doc:`compute <compute>` command
+* pair = style name of this compute command
+* pstyle = style name of a pair style that calculates additional values
+* evalue = *epair* or *evdwl* or *ecoul* or blank (optional setting)
+
+Examples
+""""""""
+
+.. parsed-literal::
+
+   compute 1 all pair gauss
+   compute 1 all pair lj/cut/coul/cut ecoul
+   compute 1 all pair reax
+
+Description
+"""""""""""
+
+Define a computation that extracts additional values calculated by a
+pair style, and makes them accessible for output or further processing
+by other commands.  The group specified for this command is ignored.
+
+The specified *pstyle* must be a pair style used in your simulation
+either by itself or as a sub-style in a :doc:`pair_style hybrid or hybrid/overlay <pair_hybrid>` command.
+
+The *evalue* setting is optional; it may be left off the command.  All
+pair styles tally a potential energy *epair* which may be broken into
+two parts: *evdwl* and *ecoul* such that *epair* = *evdwl* + *ecoul*\ .
+If the pair style calculates Coulombic interactions, their energy will
+be tallied in *ecoul*\ .  Everything else (whether it is a Lennard-Jones
+style van der Waals interaction or not) is tallied in *evdwl*\ .  If
+*evalue* is specified as *epair* or left out, then *epair* is stored
+as a global scalar by this compute.  This is useful when using
+:doc:`pair_style hybrid <pair_hybrid>` if you want to know the portion
+of the total energy contributed by one sub-style.  If *evalue* is
+specfied as *evdwl* or *ecoul*\ , then just that portion of the energy
+is stored as a global scalar.
+
+.. note::
+
+   The energy returned by the *evdwl* keyword does not include tail
+   corrections, even if they are enabled via the
+   :doc:`pair_modify <pair_modify>` command.
+
+Some pair styles tally additional quantities, e.g. a breakdown of
+potential energy into a dozen or so components is tallied by the
+:doc:`pair_style reax <pair_reax>` commmand.  These values (1 or more)
+are stored as a global vector by this compute.  See the doc page for
+:doc:`individual pair styles <pair_style>` for info on these values.
+
+**Output info:**
+
+This compute calculates a global scalar which is *epair* or *evdwl* or
+*ecoul*\ .  If the pair style supports it, it also calculates a global
+vector of length >= 1, as determined by the pair style.  These values
+can be used by any command that uses global scalar or vector values
+from a compute as input.  See :ref:`this section <howto_15>` for an overview of LAMMPS output
+options.
+
+The scalar and vector values calculated by this compute are
+"extensive".
+
+The scalar value will be in energy :doc:`units <units>`.  The vector
+values will typically also be in energy :doc:`units <units>`, but see
+the doc page for the pair style for details.
+
+Restrictions
+""""""""""""
+ none
+
+Related commands
+""""""""""""""""
+
+:doc:`compute pe <compute_pe>`, :doc:`compute bond <compute_bond>`
+
+Default
+"""""""
+
+The default for *evalue* is *epair*\ .
+
+
+.. _lws: http://lammps.sandia.gov
+.. _ld: Manual.html
+.. _lc: Section_commands.html#comm