Merge pull request #1841 from phankl/stable

   * :doc:`meam/c <pair_meamc>`

   * :doc:`meam/spline (o) <pair_meam_spline>`

   * :doc:`meam/sw/spline <pair_meam_sw_spline>`

   * :doc:`mesocnt <pair_mesocnt>`

   * :doc:`mgpt <pair_mgpt>`

   * :doc:`mie/cut (g) <pair_mie>`

   * :doc:`mm3/switch3/coulgauss/long <pair_mm3_switch3_coulgauss_long>`

   * :doc:`yukawa/colloid (go) <pair_yukawa_colloid>`

   * :doc:`zbl (gko) <pair_zbl>`

   *

   *

.. index:: pair\_style mesocnt

pair\_style mesocnt command

===========================

Syntax

""""""

.. parsed-literal::

   pair_style mesocnt

Examples

""""""""

.. parsed-literal::

   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::

   LAMMPS comes with one *mesocnt* style potential file

   where the default number of data points per table is 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 USER-MISC package.  It is only

enabled if LAMMPS was built with that package.  See the :doc:`Build package <Build_package>` doc 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).

.. _lws: http://lammps.sandia.gov

.. _ld: Manual.html

.. _lc: Commands_all.html

* :doc:`meam/c <pair_meamc>` - modified embedded atom method (MEAM) in C

* :doc:`meam/spline <pair_meam_spline>` - splined version of MEAM

* :doc:`meam/sw/spline <pair_meam_sw_spline>` - splined version of MEAM with a Stillinger-Weber term

* :doc:`mesocnt <pair_mesocnt>` - mesoscale model for (carbon) nanotubes

* :doc:`mgpt <pair_mgpt>` - simplified model generalized pseudopotential theory (MGPT) potential

* :doc:`mie/cut <pair_mie>` - Mie potential

* :doc:`mm3/switch3/coulgauss/long <pair_mm3_switch3_coulgauss_long>` - smoothed MM3 vdW potential with Gaussian electrostatics

Merz

meshless

meso

mesocnt

mesoparticle

mesoscale

mesoscopic

Silbert

Silling

Sim

Simov

Simul

simulations

Sinnott

ufm

Uhlenbeck

Ui

uInfParallel

uk

ul

ulb

Urbakh

Urbana

usec

uSemiParallel

userguide

username

usr

vn

Voigt

volfactor

Volkov

Volpe

volpress

volumetric

Zhang

Zhen

zhi

Zhigilei

Zhou

Zhu

zi

../../../../potentials/C_10_10.mesocnt

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