lammps/doc/pair_meam_sw_spline.txt

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

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pair_style meam/sw/spline :h3
pair_style meam/sw/spline/omp :h3

[Syntax:]

pair_style meam/sw/spline :pre

[Examples:]

pair_style meam/sw/spline
pair_coeff * * Ti.meam.sw.spline Ti
pair_coeff * * Ti.meam.sw.spline Ti Ti Ti :pre

[Description:]

The {meam/sw/spline} style computes pairwise interactions for metals
using a variant of modified embedded-atom method (MEAM) 
potentials "(Lenosky)"_#Lenosky with an additional Stillinger-Weber (SW) 
term "(Stillinger)"_#Stillinger in the energy.  This form of the
potential was first proposed 
by Nicklas, Fellinger, and Park "(Nicklas)"_#Nicklas.  
We refer to it as MEAM+SW.  The total energy E is given by

:c,image(pair_meam_sw_spline.jpg)

where rho_I is the density at atom I, theta_JIK is the angle between 
atoms J, I, and K centered on atom I. The seven functions 
Phi, F, G, U, rho, f, and g are represented by cubic splines.

The cutoffs and the coefficients for these spline functions are listed 
in a parameter file which is specified by the "pair_coeff"_pair_coeff.html 
command.  Parameter files for different elements are 
included in the "potentials" directory of the LAMMPS distribution and 
have a ".meam.sw.spline" file suffix.  
All of these files are parameterized in terms of 
LAMMPS "metal units"_units.html.

Note that unlike for other potentials, cutoffs for spline-based 
MEAM+SW potentials are not set in the pair_style or pair_coeff 
command; they are specified in the potential files themselves. 

Unlike the EAM pair style, which retrieves the atomic mass from 
the potential file, the spline-based MEAM+SW potentials do not include 
mass information; thus you need to use the "mass"_mass.html
command to specify it.

Only a single pair_coeff command is used with the meam/sw/spline style 
which specifies a potential file with parameters for all needed elements. 
These are mapped to LAMMPS atom types by specifying N additional arguments 
after the filename in the pair_coeff command, where N is the number of 
LAMMPS atom types:

filename
N element names = mapping of spline-based MEAM+SW elements to atom types :ul

As an example, imagine the Ti.meam.sw.spline file has values for Ti. 
If your LAMMPS simulation has 3 atoms types and they are all to be 
treated with this potential, you would use the following pair_coeff command:

pair_coeff * * Ti.meam.sw.spline Ti Ti Ti

The 1st 2 arguments must be * * so as to span all LAMMPS atom types. 
The three Ti arguments map LAMMPS atom types 1,2,3 to the Ti element 
in the potential file. If a mapping value is specified as NULL, the 
mapping is not performed. This can be used when a {meam/sw/spline} 
potential is used as part of the hybrid pair style. The NULL values 
are placeholders for atom types that will be used with other potentials. 

IMPORTANT NOTE: The {meam/sw/spline} style currently supports only 
single-element MEAM+SW potentials.  It may be extended for alloy systems 
in the future. 

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[Mixing, shift, table, tail correction, restart, rRESPA info]:

The pair style does not support multiple element types or mixing. 
It has been designed for pure elements only.

This pair style does not support the "pair_modify"_pair_modify.html
shift, table, and tail options.

The {meam/sw/spline} pair style does not write its information to 
"binary restart files"_restart.html, since it is stored in an external 
potential parameter file.  Thus, you need to re-specify the pair_style 
and pair_coeff commands in an input script that reads a restart file.

The {meam/sw/spline} pair style can only be used via the {pair} keyword of the
"run_style respa"_run_style.html command.  They do not support the
{inner}, {middle}, {outer} keywords.

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[Restrictions:]

This pair style requires the "newton"_newton.html setting to be "on"
for pair interactions.

This pair style is only enabled if LAMMPS was built with the USER-MISC package.
See the "Making LAMMPS"_Section_start.html#start_3 section for more info.

[Related commands:]

"pair_coeff"_pair_coeff.html "pair_style meam"_pair_meam.html "pair_style meam/spline"_pair_meam_spline.html

[Default:] none

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:link(Lenosky)
[(Lenosky)] Lenosky, Sadigh, Alonso, Bulatov, de la Rubia, Kim, Voter, Kress, Modell. Simul. Mater. Sci. Eng. 8, 825 (2000).

:link(Stillinger)
[(Stillinger)] Stillinger, Weber, Phys. Rev. B 31, 5262 (1985).

:link(Nicklas)
[(Nicklas)] 
The spline-based MEAM+SW format was first devised and used to develop
potentials for bcc transition metals by Jeremy Nicklas, Michael Fellinger,
and Hyoungki Park at The Ohio State University.