forked from lijiext/lammps
135 lines
5.0 KiB
Plaintext
135 lines
5.0 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 ufm command :h3
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pair_style ufm/gpu command :h3
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pair_style ufm/omp command :h3
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pair_style ufm/opt command :h3
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[Syntax:]
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pair_style ufm cutoff :pre
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cutoff = global cutoff for {ufm} interactions (distance units) :ul
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[Examples:]
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pair_style ufm 4.0
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pair_coeff 1 1 100.0 1.0 2.5
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pair_coeff * * 100.0 1.0 :pre
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pair_style ufm 4.0
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pair_coeff * * 10.0 1.0
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variable prefactor equal ramp(10,100)
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fix 1 all adapt 1 pair ufm epsilon * * v_prefactor :pre
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[Description:]
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Style {ufm} computes pairwise interactions using the Uhlenbeck-Ford model (UFM) potential "(Paula Leite2016)"_#PL2 which is given by
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:c,image(Eqs/pair_ufm.jpg)
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where rc is the cutoff, sigma is a distance-scale and epsilon is an energy-scale, i.e., a product of Boltzmann constant kB, temperature T and the Uhlenbeck-Ford p-parameter which is responsible
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to control the softness of the interactions "(Paula Leite2017)"_#PL1.
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This model is useful as a reference system for fluid-phase free-energy calculations "(Paula Leite2016)"_#PL2.
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The following coefficients must be defined for each pair of atom types
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via the "pair_coeff"_pair_coeff.html command as in the examples above,
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or in the data file or restart files read by the
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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands, or by mixing as described below:
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epsilon (energy units)
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sigma (distance units)
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cutoff (distance units) :ul
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The last coefficient is optional. If not specified, the global {ufm}
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cutoff is used.
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The "fix adapt"_fix_adapt.html command can be used to vary epsilon and sigma for this pair style over the course of a simulation, in which case
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pair_coeff settings for epsilon and sigma must still be specified, but will be
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overridden. For example these commands will vary the prefactor epsilon for
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all pairwise interactions from 10.0 at the beginning to 100.0 at the end
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of a run:
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variable prefactor equal ramp(10,100)
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fix 1 all adapt 1 pair ufm epsilon * * v_prefactor :pre
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NOTE: The thermodynamic integration procedure can be performed with this potential using "fix adapt"_fix_adapt.html. This command will rescale the force on each atom by varying a scale variable, which always starts with value 1.0. The syntax is the same described above, however, changing epsilon to scale. A detailed explanation of how to use this command and perform nonequilibrium thermodynamic integration in LAMMPS is given in the paper by "(Freitas)"_#Freitas2.
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:line
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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 "Speed packages"_Speed_packages.html 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 "Build
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package"_Build_package.html 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 "-suffix command-line
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switch"_Run_options.html when you invoke LAMMPS, or you can use the
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"suffix"_suffix.html command in your input script.
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See the "Speed packages"_Speed_packages.html doc page for more
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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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For atom type pairs I,J and I != J, the A coefficient and cutoff
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distance for this pair style can be mixed. A is always mixed via a
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{geometric} rule. The cutoff is mixed according to the pair_modify
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mix value. The default mix value is {geometric}. See the
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"pair_modify" command for details.
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This pair style support the "pair_modify"_pair_modify.html shift option for the energy of the pair interaction.
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The "pair_modify"_pair_modify.html table and tail are not relevant for this
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pair style.
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This pair style does not support the "pair_modify"_pair_modify.html tail option for adding long-range tail corrections to energy and pressure.
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This pair style writes its 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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This pair style can only be used via the {pair} keyword of the
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"run_style respa"_run_style.html command. It does not support the
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{inner}, {middle}, {outer} keywords.
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:line
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[Restrictions:] none
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "fix adapt"_fix_adapt.html
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[Default:] none
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:link(PL1)
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[(Paula Leite2017)] Paula Leite, Santos-Florez, and de Koning, Phys Rev E, 96,
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32115 (2017).
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:link(PL2)
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[(Paula Leite2016)] Paula Leite , Freitas, Azevedo, and de Koning, J Chem Phys, 126,
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044509 (2016).
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:link(Freitas2)
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[(Freitas)] Freitas, Asta, and de Koning, Computational Materials Science, 112, 333 (2016).
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