41 lines
1.7 KiB
ReStructuredText
41 lines
1.7 KiB
ReStructuredText
Variable options
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================
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The ``Variable`` class computes and stores :doc:`variable <variable>`
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information in LAMMPS; see the file ``variable.cpp``. The value
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associated with a variable can be periodically printed to the screen
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via the :doc:`print <print>`, :doc:`fix print <fix_print>`, or
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:doc:`thermo_style custom <thermo_style>` commands. Variables of style
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"equal" can compute complex equations that involve the following types
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of arguments:
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.. parsed-literal::
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thermo keywords = ke, vol, atoms, ...
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other variables = v_a, v_myvar, ...
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math functions = div(x,y), mult(x,y), add(x,y), ...
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group functions = mass(group), xcm(group,x), ...
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atom values = x[123], y[3], vx[34], ...
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compute values = c_mytemp[0], c_thermo_press[3], ...
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Adding keywords for the :doc:`thermo_style custom <thermo_style>`
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command (which can then be accessed by variables) is discussed in the
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:doc:`Modify thermo <Modify_thermo>` documentation.
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Adding a new math function of one or two arguments can be done by
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editing one section of the ``Variable::evaluate()`` method. Search for
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the word "customize" to find the appropriate location.
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Adding a new group function can be done by editing one section of the
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``Variable::evaluate()`` method. Search for the word "customize" to
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find the appropriate location. You may need to add a new method to the
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Group class as well (see the ``group.cpp`` file).
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Accessing a new atom-based vector can be done by editing one section
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of the Variable::evaluate() method. Search for the word "customize"
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to find the appropriate location.
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Adding new :doc:`compute styles <compute>` (whose calculated values can
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then be accessed by variables) is discussed in the :doc:`Modify compute
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<Modify_compute>` documentation.
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