234 lines
7.7 KiB
ReStructuredText
234 lines
7.7 KiB
ReStructuredText
.. index:: pair\_style born
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pair\_style born command
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========================
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pair\_style born/omp command
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============================
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pair\_style born/gpu command
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============================
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pair\_style born/coul/long command
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==================================
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pair\_style born/coul/long/gpu command
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======================================
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pair\_style born/coul/long/omp command
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======================================
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pair\_style born/coul/msm command
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=================================
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pair\_style born/coul/msm/omp command
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=====================================
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pair\_style born/coul/wolf command
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==================================
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pair\_style born/coul/wolf/gpu command
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======================================
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pair\_style born/coul/wolf/omp command
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======================================
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pair\_style born/coul/dsf command
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=================================
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Syntax
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""""""
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.. parsed-literal::
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pair_style style args
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* style = *born* or *born/coul/long* or *born/coul/msm* or *born/coul/wolf*
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* args = list of arguments for a particular style
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.. parsed-literal::
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*born* args = cutoff
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cutoff = global cutoff for non-Coulombic interactions (distance units)
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*born/coul/long* args = cutoff (cutoff2)
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cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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*born/coul/msm* args = cutoff (cutoff2)
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cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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*born/coul/wolf* args = alpha cutoff (cutoff2)
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alpha = damping parameter (inverse distance units)
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cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (optional) (distance units)
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*born/coul/dsf* args = alpha cutoff (cutoff2)
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alpha = damping parameter (inverse distance units)
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cutoff = global cutoff for non-Coulombic (and Coulombic if only 1 arg) (distance units)
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cutoff2 = global cutoff for Coulombic (distance units)
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Examples
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""""""""
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.. parsed-literal::
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pair_style born 10.0
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pair_coeff \* \* 6.08 0.317 2.340 24.18 11.51
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pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
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pair_style born/coul/long 10.0
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pair_style born/coul/long 10.0 8.
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pair_coeff \* \* 6.08 0.317 2.340 24.18 11.51
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pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
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pair_style born/coul/msm 10.0
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pair_style born/coul/msm 10.0 8.0
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pair_coeff \* \* 6.08 0.317 2.340 24.18 11.51
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pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
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pair_style born/coul/wolf 0.25 10.0
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pair_style born/coul/wolf 0.25 10.0 9.0
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pair_coeff \* \* 6.08 0.317 2.340 24.18 11.51
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pair_coeff 1 1 6.08 0.317 2.340 24.18 11.51
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pair_style born/coul/dsf 0.1 10.0 12.0
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pair_coeff \* \* 0.0 1.00 0.00 0.00 0.00
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pair_coeff 1 1 480.0 0.25 0.00 1.05 0.50
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Description
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"""""""""""
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The *born* style computes the Born-Mayer-Huggins or Tosi/Fumi
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potential described in :ref:`(Fumi and Tosi) <FumiTosi>`, given by
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.. image:: Eqs/pair_born.jpg
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:align: center
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where sigma is an interaction-dependent length parameter, rho is an
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ionic-pair dependent length parameter, and Rc is the cutoff.
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The styles with *coul/long* or *coul/msm* add a Coulombic term as
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described for the :doc:`lj/cut <pair_lj>` pair styles. An additional
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damping factor is applied to the Coulombic term so it can be used in
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conjunction with the :doc:`kspace_style <kspace_style>` command and its
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*ewald* or *pppm* of *msm* option. The Coulombic cutoff specified for
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this style means that pairwise interactions within this distance are
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computed directly; interactions outside that distance are computed in
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reciprocal space.
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If one cutoff is specified for the *born/coul/long* and
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*born/coul/msm* style, it is used for both the A,C,D and Coulombic
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terms. If two cutoffs are specified, the first is used as the cutoff
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for the A,C,D terms, and the second is the cutoff for the Coulombic
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term.
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The *born/coul/wolf* style adds a Coulombic term as described for the
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Wolf potential in the :doc:`coul/wolf <pair_coul>` pair style.
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The *born/coul/dsf* style computes the Coulomb contribution with the
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damped shifted force model as in the :doc:`coul/dsf <pair_coul>` style.
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Note that these potentials are related to the :doc:`Buckingham potential <pair_buck>`.
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The following coefficients must be defined for each pair of atoms
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types via the :doc:`pair_coeff <pair_coeff>` command as in the examples
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above, or in the data file or restart files read by the
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:doc:`read_data <read_data>` or :doc:`read_restart <read_restart>`
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commands, or by mixing as described below:
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* A (energy units)
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* rho (distance units)
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* sigma (distance units)
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* C (energy units \* distance units\^6)
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* D (energy units \* distance units\^8)
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* cutoff (distance units)
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The second coefficient, rho, must be greater than zero.
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The last coefficient is optional. If not specified, the global A,C,D
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cutoff specified in the pair\_style command is used.
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For *born/coul/long*\ , *born/coul/wolf* and *born/coul/dsf* no
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Coulombic cutoff can be specified for an individual I,J type pair.
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All type pairs use the same global Coulombic cutoff specified in the
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pair\_style command.
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----------
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Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed on the :doc:`Speed packages <Speed_packages>` doc
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page. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the :doc:`Build package <Build_package>` doc page for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the :doc:`-suffix command-line switch <Run_options>` when you invoke LAMMPS, or you can use the
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:doc:`suffix <suffix>` command in your input script.
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See the :doc:`Speed packages <Speed_packages>` doc page for more
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instructions on how to use the accelerated styles effectively.
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----------
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**Mixing, shift, table, tail correction, restart, rRESPA info**\ :
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These pair styles do not support mixing. Thus, coefficients for all
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I,J pairs must be specified explicitly.
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These styles support the :doc:`pair_modify <pair_modify>` shift option
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for the energy of the exp(), 1/r\^6, and 1/r\^8 portion of the pair
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interaction.
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The *born/coul/long* pair style supports the
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:doc:`pair_modify <pair_modify>` table option to tabulate the
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short-range portion of the long-range Coulombic interaction.
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These styles support the pair\_modify tail option for adding long-range
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tail corrections to energy and pressure.
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Thess styles writes thei information to binary :doc:`restart <restart>`
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files, so pair\_style and pair\_coeff commands do not need to be
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specified in an input script that reads a restart file.
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These styles can only be used via the *pair* keyword of the :doc:`run_style respa <run_style>` command. They do not support the *inner*\ ,
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*middle*\ , *outer* keywords.
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----------
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Restrictions
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""""""""""""
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The *born/coul/long* style is part of the KSPACE package. It is only
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enabled if LAMMPS was built with that package. See the :doc:`Build package <Build_package>` doc page for more info.
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Related commands
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""""""""""""""""
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:doc:`pair_coeff <pair_coeff>`, :doc:`pair_style buck <pair_buck>`
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**Default:** none
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----------
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.. _FumiTosi:
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Fumi and Tosi, J Phys Chem Solids, 25, 31 (1964),
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Fumi and Tosi, J Phys Chem Solids, 25, 45 (1964).
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