forked from lijiext/lammps
155 lines
5.4 KiB
Plaintext
155 lines
5.4 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,Section_commands.html#comm)
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:line
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pair_style yukawa/colloid command :h3
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pair_style yukawa/colloid/gpu command :h3
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pair_style yukawa/colloid/omp command :h3
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[Syntax:]
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pair_style yukawa/colloid kappa cutoff :pre
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kappa = screening length (inverse distance units)
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cutoff = global cutoff for colloidal Yukawa interactions (distance units) :ul
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[Examples:]
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pair_style yukawa/colloid 2.0 2.5
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pair_coeff 1 1 100.0 2.3
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pair_coeff * * 100.0 :pre
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[Description:]
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Style {yukawa/colloid} computes pairwise interactions with the formula
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:c,image(Eqs/pair_yukawa_colloid.jpg)
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where Ri and Rj are the radii of the two particles and Rc is the
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cutoff.
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In contrast to "pair_style yukawa"_pair_yukawa.html, this functional
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form arises from the Coulombic interaction between two colloid
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particles, screened due to the presence of an electrolyte, see the
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book by "Safran"_#Safran for a derivation in the context of DVLO
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theory. "Pair_style yukawa"_pair_yukawa.html is a screened Coulombic
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potential between two point-charges and uses no such approximation.
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This potential applies to nearby particle pairs for which the Derjagin
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approximation holds, meaning h << Ri + Rj, where h is the
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surface-to-surface separation of the two particles.
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When used in combination with "pair_style colloid"_pair_colloid.html,
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the two terms become the so-called DLVO potential, which combines
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electrostatic repulsion and van der Waals attraction.
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The following coefficients must be defined for each pair of atoms
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types via the "pair_coeff"_pair_coeff.html 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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"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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A (energy/distance units)
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cutoff (distance units) :ul
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The prefactor A is determined from the relationship between surface
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charge and surface potential due to the presence of electrolyte. Note
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that the A for this potential style has different units than the A
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used in "pair_style yukawa"_pair_yukawa.html. For low surface
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potentials, i.e. less than about 25 mV, A can be written as:
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A = 2 * PI * R*eps*eps0 * kappa * psi^2 :pre
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where
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R = colloid radius (distance units)
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eps0 = permittivity of free space (charge^2/energy/distance units)
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eps = relative permittivity of fluid medium (dimensionless)
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kappa = inverse screening length (1/distance units)
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psi = surface potential (energy/charge units) :ul
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The last coefficient is optional. If not specified, the global
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yukawa/colloid cutoff is used.
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:line
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Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally
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the same as the corresponding style without the suffix. They have
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been optimized to run faster, depending on your available hardware, as
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discussed in "Section_accelerate"_Section_accelerate.html of the
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manual. 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 USER-CUDA, GPU, USER-OMP and OPT
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packages, respectively. They are only enabled if LAMMPS was built with
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those packages. See the "Making LAMMPS"_Section_start.html#start_3
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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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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 an energy value mixed
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like a LJ epsilon. The default mix value is {geometric}. See the
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"pair_modify" command for details.
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This pair style supports the "pair_modify"_pair_modify.html shift
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option for the energy of the pair interaction.
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The "pair_modify"_pair_modify.html table option is not relevant
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for this pair style.
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This pair style does not support the "pair_modify"_pair_modify.html
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tail option for adding long-range tail corrections to energy and
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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:]
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This style is part of the COLLOID package. It is only enabled if
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LAMMPS was built with that package. See the "Making
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LAMMPS"_Section_start.html#start_3 section for more info.
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This pair style requires that atoms be finite-size spheres with a
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diameter, as defined by the "atom_style sphere"_atom_style.html
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command.
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Per-particle polydispersity is not yet supported by this pair style;
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per-type polydispersity is allowed. This means all particles of the
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same type must have the same diameter. Each type can have a different
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diameter.
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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(Safran)
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[(Safran)] Safran, Statistical Thermodynamics of Surfaces, Interfaces,
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And Membranes, Westview Press, ISBN: 978-0813340791 (2003).
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