forked from lijiext/lammps
158 lines
4.4 KiB
Plaintext
158 lines
4.4 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,Commands_all.html)
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:line
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pair_style lj/mdf command :h3
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pair_style buck/mdf command :h3
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pair_style lennard/mdf command :h3
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[Syntax:]
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pair_style style args :pre
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style = {lj/mdf} or {buck/mdf} or {lennard/mdf} :ulb,l
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args = list of arguments for a particular style :l
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{lj/mdf} args = cutoff1 cutoff2
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cutoff1 = inner cutoff for the start of the tapering function
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cutoff1 = out cutoff for the end of the tapering function
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{buck/mdf} args = cutoff1 cutoff2
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cutoff1 = inner cutoff for the start of the tapering function
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cutoff1 = out cutoff for the end of the tapering function
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{lennard/mdf} args = cutoff1 cutoff2
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cutoff1 = inner cutoff for the start of the tapering function
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cutoff1 = out cutoff for the end of the tapering function :pre
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:ule
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[Examples:]
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pair_style lj/mdf 2.5 3.0
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pair_coeff * * 1.0 1.0
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pair_coeff 1 1 1.1 2.8 3.0 3.2 :pre
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pair_style buck 2.5 3.0
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pair_coeff * * 100.0 1.5 200.0
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pair_coeff * * 100.0 1.5 200.0 3.0 3.5 :pre
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pair_style lennard/mdf 2.5 3.0
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pair_coeff * * 1.0 1.0
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pair_coeff 1 1 1021760.3664 2120.317338 3.0 3.2 :pre
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[Description:]
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The {lj/mdf}, {buck/mdf} and {lennard/mdf} compute the standard 12-6
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Lennard-Jones and Buckingham potential with the addition of a taper
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function that ramps the energy and force smoothly to zero between an
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inner and outer cutoff.
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:c,image(Eqs/pair_mdf-1.jpg)
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The tapering, {f(r)}, is done by using the Mei, Davenport, Fernando
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function "(Mei)"_#Mei.
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:c,image(Eqs/pair_mdf-2.jpg)
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where
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:c,image(Eqs/pair_mdf-3.jpg)
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Here {r_m} is the inner cutoff radius and {r_cut} is the outer cutoff
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radius.
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:line
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For the {lj/mdf} pair_style, the potential energy, {E(r)}, is the
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standard 12-6 Lennard-Jones written in the epsilon/sigma form:
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:c,image(Eqs/pair_mdf-4.jpg)
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Either the first two or all of the following coefficients must be
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defined for each pair of atoms types via the pair_coeff command as
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in the examples above, or in the data file read by the
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"read_data"_read_data.html. The two cutoffs default to the global
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values and epsilon and sigma can also be determined by mixing as
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described below:
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epsilon (energy units)
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sigma (distance units)
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r_m (distance units)
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r_{cut} (distance units) :ul
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:line
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For the {buck/mdf} pair_style, the potential energy, {E(r)}, is the
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standard Buckingham potential with three required coefficients.
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The two cutoffs can be omitted and default to the corresponding
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global values:
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:c,image(Eqs/pair_mdf-5.jpg)
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A (energy units)
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\rho (distance units)
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C (energy-distance^6 units)
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r_m (distance units)
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r_{cut} (distance units) :ul
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:line
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For the {lennard/mdf} pair_style, the potential energy, {E(r)}, is the
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standard 12-6 Lennard-Jones written in the A/B form:
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:c,image(Eqs/pair_mdf-6.jpg)
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The following coefficients must be defined for each pair of atoms
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types via the pair_coeff command as in the examples above, or in the
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data file read by the read_data commands, or by mixing as described below.
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The two cutoffs default to their global values and must be either both
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given or both left out:
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A (energy-distance^12 units)
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B (energy-distance^6 units)
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r_m (distance units)
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r_{cut} (distance units) :ul
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:line
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[Mixing, shift, table, tail correction, restart, rRESPA info]:
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For atom type pairs I,J and I != J, the epsilon and sigma coefficients
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and cutoff distances for the lj/mdf pair style can be mixed.
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The default mix value is {geometric}. See the "pair_modify" command
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for details. The other two pair styles buck/mdf and lennard/mdf do not
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support mixing, so all I,J pairs of coefficients must be specified
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explicitly.
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None of the lj/mdf, buck/mdf, or lennard/mdf pair styles supports
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the "pair_modify"_pair_modify.html shift option or long-range
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tail corrections to pressure and energy.
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These styles write their information to "binary restart
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files"_restart.html, so pair_style and pair_coeff commands do not need
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to be 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 "run_style
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respa"_run_style.html command. They do not support the {inner},
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{middle}, {outer} keywords.
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:line
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[Restrictions:]
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These pair styles can only be used if LAMMPS was built with the
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USER-MISC package. See the "Build package"_Build_package.html doc
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page for more info.
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[Related commands:]
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"pair_coeff"_pair_coeff.html
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[Default:] none
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:line
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:link(Mei)
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[(Mei)] Mei, Davenport, Fernando, Phys Rev B, 43 4653 (1991)
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