forked from lijiext/lammps
112 lines
3.6 KiB
Plaintext
112 lines
3.6 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 coul/diel command :h3
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[Syntax:]
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pair_style coul/diel cutoff :pre
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cutoff = global cutoff (distance units)
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[Examples:]
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pair_style coul/diel 3.5
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pair_coeff 1 4 78. 1.375 0.112 :pre
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[Description:]
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Style {coul/diel} computes a Coulomb correction for implict solvent
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ion interactions in which the dielectric perimittivity is distance dependent.
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The dielectric permittivity epsilon_D(r) connects to limiting regimes:
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One limit is defined by a small dielectric permittivity (close to vacuum)
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at or close to contact seperation between the ions. At larger separations
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the dielectric permittivity reaches a bulk value used in the regular Coulomb
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interaction coul/long or coul/cut.
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The transition is modeled by a hyperbolic function which is incorporated
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in the Coulomb correction term for small ion separations as follows
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:c,image(Eqs/pair_coul_diel.jpg)
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where r_me is the inflection point of epsilon_D(r) and sigma_e is a slope
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defining length scale. C is the same Coulomb conversion factor as in the
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pair_styles coul/cut, coul/long, and coul/debye. In this way the Coulomb
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interaction between ions is corrected at small distances r. The lower
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limit of epsilon_D(r->0)=5.2 due to dielectric saturation "(Stiles)"_#Stiles
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while the Coulomb interaction reaches its bulk limit by setting
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epsilon_D(r->\infty)=epsilon, the bulk value of the solvent which is 78
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for water at 298K.
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Examples of the use of this type of Coulomb interaction include implicit
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solvent simulations of salt ions
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"(Lenart)"_#Lenart and of ionic surfactants "(Jusufi)"_#Jusufi.
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Note that this potential is only reasonable for implicit solvent simulations
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and in combiantion with coul/cut or coul/long. It is also usually combined
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with gauss/cut, see "(Lenart)"_#Lenart or "(Jusufi)"_#Jusufi.
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The following coefficients must be defined for each pair of atom
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types via the "pair_coeff"_pair_coeff.html command as in the example
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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:
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epsilon (no units)
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r_me (distance units)
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sigma_e (distance units) :ul
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The global cutoff (r_c) specified in the pair_style command is used.
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:line
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[Mixing, shift, table, tail correction, restart, rRESPA info]:
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This pair style does not support parameter mixing. Coefficients must be given explicitly for each type of particle pairs.
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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 Gauss-potential portion of the pair
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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 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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[Restrictions:]
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This style is part of the "user-misc" package. It is only enabled
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if LAMMPS was built with that package. See the "Making
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LAMMPS"_Section_start.html#2_3 section for more info.
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[Related commands:]
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"pair_coeff"_pair_coeff.html
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"pair_style gauss/cut"_pair_gauss.html
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[Default:] none
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:line
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:link(Stiles)
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[(Stiles)] Stiles , Hubbard, and Kayser, J Chem Phys, 77,
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6189 (1982).
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:link(Lenart)
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[(Lenart)] Lenart , Jusufi, and Panagiotopoulos, J Chem Phys, 126,
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044509 (2007).
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:link(Jusufi)
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[(Jusufi)] Jusufi, Hynninen, and Panagiotopoulos, J Phys Chem B, 112,
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13783 (2008).
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