forked from lijiext/lammps
145 lines
5.2 KiB
Plaintext
145 lines
5.2 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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pair_style meam/spline :h3
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pair_style meam/spline/omp :h3
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[Syntax:]
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pair_style meam/spline :pre
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[Examples:]
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pair_style meam/spline
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pair_coeff * * Ti.meam.spline Ti
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pair_coeff * * Ti.meam.spline Ti Ti Ti :pre
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[Description:]
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The {meam/spline} style computes pairwise interactions for metals
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using a variant of modified embedded-atom method (MEAM) potentials
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"(Lenosky)"_#Lenosky. The total energy E is given by
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:c,image(Eqs/pair_meam_spline.jpg)
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where rho_i is the density at atom I, theta_jik is the angle between
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atoms J, I, and K centered on atom I. The five functions Phi, U, rho,
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f, and g are represented by cubic splines.
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The cutoffs and the coefficients for these spline functions are listed
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in a parameter file which is specified by the
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"pair_coeff"_pair_coeff.html command. Parameter files for different
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elements are included in the "potentials" directory of the LAMMPS
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distribution and have a ".meam.spline" file suffix. All of these
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files are parameterized in terms of LAMMPS "metal units"_units.html.
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Note that unlike for other potentials, cutoffs for spline-based MEAM
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potentials are not set in the pair_style or pair_coeff command; they
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are specified in the potential files themselves.
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Unlike the EAM pair style, which retrieves the atomic mass from the
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potential file, the spline-based MEAM potentials do not include mass
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information; thus you need to use the "mass"_mass.html command to
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specify it.
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Only a single pair_coeff command is used with the {meam/spline} style
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which specifies a potential file with parameters for all needed
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elements. These are mapped to LAMMPS atom types by specifying N
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additional arguments after the filename in the pair_coeff command,
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where N is the number of LAMMPS atom types:
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filename
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N element names = mapping of spline-based MEAM elements to atom types :ul
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See the "pair_coeff"_pair_coeff.html doc page for alternate ways
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to specify the path for the potential file.
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As an example, imagine the Ti.meam.spline file has values for Ti. If
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your LAMMPS simulation has 3 atoms types and they are all to be
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treated with this potentials, you would use the following pair_coeff
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command:
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pair_coeff * * Ti.meam.spline Ti Ti Ti :pre
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The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
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The three Ti arguments map LAMMPS atom types 1,2,3 to the Ti element
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in the potential file. If a mapping value is specified as NULL, the
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mapping is not performed. This can be used when a {meam/spline}
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potential is used as part of the {hybrid} pair style. The NULL values
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are placeholders for atom types that will be used with other
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potentials.
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NOTE: The {meam/spline} style currently supports only single-element
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MEAM potentials. It may be extended for alloy systems in the future.
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:line
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Styles with a {cuda}, {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 in "Section_accelerate"_Section_accelerate.html
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of the manual. The accelerated styles take the same arguments and
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should produce the same results, except for round-off and precision
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issues.
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These accelerated styles are part of the USER-CUDA, GPU, USER-INTEL,
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KOKKOS, USER-OMP and OPT packages, respectively. They are only
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enabled if LAMMPS was built with those packages. See the "Making
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LAMMPS"_Section_start.html#start_3 section 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 "-suffix command-line
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switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
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use the "suffix"_suffix.html command in your input script.
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See "Section_accelerate"_Section_accelerate.html of the manual for
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more instructions on how to use the accelerated styles effectively.
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:line
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[Mixing, shift, table, tail correction, restart, rRESPA info]:
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The current version of this pair style does not support multiple
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element types or mixing. It has been designed for pure elements only.
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This pair style does not support the "pair_modify"_pair_modify.html
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shift, table, and tail options.
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The {meam/spline} pair style does not write its information to "binary
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restart files"_restart.html, since it is stored in an external
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potential parameter file. Thus, you need to re-specify the pair_style
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and pair_coeff commands in an input script that reads a restart file.
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The {meam/spline} pair style can only be used via the {pair} keyword of the
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"run_style respa"_run_style.html command. They do not support the
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{inner}, {middle}, {outer} keywords.
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:line
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[Restrictions:]
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This pair style requires the "newton"_newton.html setting to be "on"
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for pair interactions.
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This pair style is only enabled if LAMMPS was built with the USER-MISC
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package. See the "Making LAMMPS"_Section_start.html#start_3 section
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for more info.
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "pair_style meam"_pair_meam.html
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[Default:] none
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:line
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:link(Lenosky)
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[(Lenosky)] Lenosky, Sadigh, Alonso, Bulatov, de la Rubia, Kim, Voter,
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Kress, Modelling Simulation Materials Science Enginerring, 8, 825
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(2000).
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