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Add use instructions and examples for NCrystal

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Jose Ignacio Marquez Damian 2022-11-10 13:04:47 -03:00 • committed by GitHub
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docs/source/usersguide/materials.rst
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@ -101,6 +101,42 @@ you would need to add hydrogen and oxygen to a material and then assign the
.. _usersguide_naming:
------------------
Adding NCrystal materials
------------------
Additional support for thermal scattering can be added by using NCrystal_.
The :meth:`Material.from_ncrystal` class method generates a material object from
an `NCrystal configuration string <https://github.com/mctools/ncrystal/wiki/Using-NCrystal#uniform-material-configuration-syntax>`_.
Temperature, material composition and density are passed from the configuration string
and the `NCMAT file <https://github.com/mctools/ncrystal/wiki/NCMAT-format>`_
that define the material, e.g:
::
mat = openmc.Material.from_ncrystal('Al_sg225.ncmat')
defines a material containing polycrystalline alumnium,
::
mat = openmc.Material.from_ncrystal(""""Ge_sg227.ncmat;dcutoff=0.5;mos=40arcsec;
dir1=@crys_hkl:5,1,1@lab:0,0,1;
dir2=@crys_hkl:0,-1,1@lab:0,1,0""")
defines an oriented germanium single crystal with 40 arcsec mosaicity.
NCrystal only handles low energy neutron interactions. Other interaction are
provided by standard ACE files. NCrystal_ comes with a `predefined library
https://github.com/mctools/ncrystal/wiki/Data-library`_ but more materials can
be added by creating NCMAT files or on-the-fly in the configuration string.
.. warning:: Currently, NCrystal_ materials cannot be modified after created.
Density, temperature and composition should be defined in the
configuration string or the NCMAT file.
.. _NCrystal: https://github.com/mctools/ncrystal
------------------
Naming Conventions
------------------
@ -222,3 +258,4 @@ been generated, you can tell OpenMC to use this file either by setting
materials.cross_sections = '/path/to/cross_sections.xml'
.. _MCNP: https://mcnp.lanl.gov/