151 lines
4.9 KiB
ReStructuredText
151 lines
4.9 KiB
ReStructuredText
.. index:: pair_style mesocnt
|
|
|
|
pair_style mesocnt command
|
|
==========================
|
|
|
|
Syntax
|
|
""""""
|
|
|
|
.. code-block:: LAMMPS
|
|
|
|
pair_style mesocnt
|
|
|
|
Examples
|
|
""""""""
|
|
|
|
.. code-block:: LAMMPS
|
|
|
|
pair_style mesocnt
|
|
pair_coeff * * 10_10.cnt
|
|
|
|
Description
|
|
"""""""""""
|
|
|
|
Style *mesocnt* implements a mesoscopic potential
|
|
for the interaction of carbon nanotubes (CNTs). In this potential,
|
|
CNTs are modelled as chains of cylindrical segments in which
|
|
each infinitesimal surface element interacts with all other
|
|
CNT surface elements with the Lennard-Jones (LJ) term adopted from
|
|
the :doc:`airebo <pair_airebo>` style. The interaction energy
|
|
is then computed by integrating over the surfaces of all interacting
|
|
CNTs.
|
|
|
|
The potential is based on interactions between one cylindrical
|
|
segment and infinitely or semi-infinitely long CNTs as described
|
|
in :ref:`(Volkov1) <Volkov1>`. Chains of segments are
|
|
converted to these (semi-)infinite CNTs bases on an approximate
|
|
chain approach outlined in :ref:`(Volkov2) <Volkov2>`.
|
|
This allows to simplify the computation of the interactions
|
|
significantly and reduces the computational times to the
|
|
same order of magnitude as for regular bead spring models
|
|
where beads interact with the standard :doc:`pair_lj/cut <pair_lj>`
|
|
potential.
|
|
|
|
In LAMMPS, cylindrical segments are represented by bonds. Each
|
|
segment is defined by its two end points ("nodes") which correspond
|
|
to atoms in LAMMPS. For the exact functional form of the potential
|
|
and implementation details, the reader is referred to the
|
|
original papers :ref:`(Volkov1) <Volkov1>` and
|
|
:ref:`(Volkov2) <Volkov2>`.
|
|
|
|
The potential requires tabulated data provided in a single ASCII
|
|
text file specified in the :doc:`pair_coeff <pair_coeff>` command.
|
|
The first line of the file provides a time stamp and
|
|
general information. The second line lists four integers giving
|
|
the number of data points provided in the subsequent four
|
|
data tables. The third line lists four floating point numbers:
|
|
the CNT radius R, the LJ parameter sigma and two numerical
|
|
parameters delta1 and delta2. These four parameters are given
|
|
in Angstroms. This is followed by four data tables each separated
|
|
by a single empty line. The first two tables have two columns
|
|
and list the parameters uInfParallel and Gamma respectively.
|
|
The last two tables have three columns giving data on a quadratic
|
|
array and list the parameters Phi and uSemiParallel respectively.
|
|
uInfParallel and uSemiParallel are given in eV/Angstrom, Phi is
|
|
given in eV and Gamma is unitless.
|
|
|
|
Potential files for CNTs can be readily generated using the freely
|
|
available code provided on
|
|
|
|
.. parsed-literal::
|
|
|
|
https://github.com/phankl/cntpot
|
|
|
|
Using the same approach, it should also be possible to
|
|
generate potential files for other 1D systems such as
|
|
boron nitride nanotubes.
|
|
|
|
.. note::
|
|
|
|
Because of their size, *mesocnt* style potential files
|
|
are not bundled with LAMMPS. When compiling LAMMPS from
|
|
source code, the file ``C_10_10.mesocnt`` should be downloaded
|
|
transparently from `https://download.lammps.org/potentials/C_10_10.mesocnt <https://download.lammps.org/potentials/C_10_10.mesocnt>`_
|
|
This file has as number of data points per table 1001.
|
|
This is sufficient for NVT simulations. For proper energy
|
|
conservation, we recommend using a potential file where
|
|
the resolution for Phi is at least 2001 data points.
|
|
|
|
.. note::
|
|
|
|
The *mesocnt* style requires CNTs to be represented
|
|
as a chain of atoms connected by bonds. Atoms need
|
|
to be numbered consecutively within one chain.
|
|
Atoms belonging to different CNTs need to be assigned
|
|
different molecule IDs.
|
|
|
|
A full summary of the method and LAMMPS implementation details
|
|
is expected to soon become available in Computer Physics
|
|
Communications.
|
|
|
|
----------
|
|
|
|
Mixing, shift, table, tail correction, restart, rRESPA info
|
|
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
|
|
|
|
This pair style does not support mixing.
|
|
|
|
This pair style does not support the :doc:`pair_modify <pair_modify>`
|
|
shift, table, and tail options.
|
|
|
|
The *mesocnt* pair style do not write their information to :doc:`binary restart files <restart>`,
|
|
since it is stored in tabulated potential files.
|
|
Thus, you need to re-specify the pair_style and pair_coeff commands in
|
|
an input script that reads a restart file.
|
|
|
|
This pair style can only be used via the *pair* keyword of the
|
|
:doc:`run_style respa <run_style>` command. They do not support the
|
|
*inner*, *middle*, *outer* keywords.
|
|
|
|
----------
|
|
|
|
Restrictions
|
|
""""""""""""
|
|
|
|
This style is part of the MESONT package. It is only
|
|
enabled if LAMMPS was built with that package. See the :doc:`Build package <Build_package>` page for more info.
|
|
|
|
This pair potential requires the :doc:`newton <newton>` setting to be
|
|
"on" for pair interactions.
|
|
|
|
Related commands
|
|
""""""""""""""""
|
|
|
|
:doc:`pair_coeff <pair_coeff>`
|
|
|
|
Default
|
|
"""""""
|
|
|
|
none
|
|
|
|
----------
|
|
|
|
.. _Volkov1:
|
|
|
|
**(Volkov1)** Volkov and Zhigilei, J Phys Chem C, 114, 5513 (2010).
|
|
|
|
.. _Volkov2:
|
|
|
|
**(Volkov2)** Volkov, Simov and Zhigilei, APS Meeting Abstracts,
|
|
Q31.013 (2008).
|