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==========================================
Setting up an OPLS force field calculation
==========================================
.. module:: ase.io.opls
:synopsis: OPLS force field
In order to facilitate the definition of structures for the use
of OPLS force fields, there are some helper classes.
Modified xyz
============
Suppose, we define the ethanal molecule as extended xyz file
(``172_ext.xyz``):
.. literalinclude:: 172_ext.xyz
Then we can read and view the structure using:
.. literalinclude:: view_172_mod.py
Defining the force field
========================
The definitions of the force field can be stored in an Amber like style
(``172_defs.par``):
.. literalinclude:: ../../../ase/test/testdata/172_defs.par
We can write LAMMPS input using the information above:
.. literalinclude:: write_lammps.py
which writes the LAMMPS input files ``lmp_atoms`` defining atoms, bonds,
etc., and ``lmp_opls`` defining the corresponding OPLS force field. A
rudimentary ``lmp_in`` is also written.
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