pair_coul.txt
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pair_coul.txt
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			"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

			:link(lws,http://lammps.sandia.gov)
			:link(ld,Manual.html)
			:link(lc,Section_commands.html#comm)

			:line

			pair_style coul/cut command :h3
			pair_style coul/cut/gpu command :h3
			pair_style coul/cut/kk command :h3
			pair_style coul/cut/omp command :h3
			pair_style coul/debye command :h3
			pair_style coul/debye/gpu command :h3
			pair_style coul/debye/kk command :h3
			pair_style coul/debye/omp command :h3
			pair_style coul/dsf command :h3
			pair_style coul/dsf/gpu command :h3
			pair_style coul/dsf/kk command :h3
			pair_style coul/dsf/omp command :h3
			pair_style coul/long command :h3
			pair_style coul/long/cs command :h3
			pair_style coul/long/omp command :h3
			pair_style coul/long/gpu command :h3
			pair_style coul/long/kk command :h3
			pair_style coul/msm command :h3
			pair_style coul/msm/omp command :h3
			pair_style coul/streitz command :h3
			pair_style coul/wolf command :h3
			pair_style coul/wolf/kk command :h3
			pair_style coul/wolf/omp command :h3
			pair_style tip4p/cut command :h3
			pair_style tip4p/long command :h3
			pair_style tip4p/cut/omp command :h3
			pair_style tip4p/long/omp command :h3

			[Syntax:]

			pair_style coul/cut cutoff
			pair_style coul/debye kappa cutoff
			pair_style coul/dsf alpha cutoff
			pair_style coul/long cutoff
			pair_style coul/long/cs cutoff
			pair_style coul/long/gpu cutoff
			pair_style coul/wolf alpha cutoff
			pair_style coul/streitz cutoff keyword alpha
			pair_style tip4p/cut otype htype btype atype qdist cutoff
			pair_style tip4p/long otype htype btype atype qdist cutoff :pre

			cutoff = global cutoff for Coulombic interactions
			kappa = Debye length (inverse distance units)
			alpha = damping parameter (inverse distance units) :ul

			[Examples:]

			pair_style coul/cut 2.5
			pair_coeff * *
			pair_coeff 2 2 3.5 :pre

			pair_style coul/debye 1.4 3.0
			pair_coeff * *
			pair_coeff 2 2 3.5 :pre

			pair_style coul/dsf 0.05 10.0
			pair_coeff * * :pre

			pair_style coul/long 10.0
			pair_style coul/long/cs 10.0
			pair_coeff * * :pre

			pair_style coul/msm 10.0
			pair_coeff * * :pre

			pair_style coul/wolf 0.2 9.0
			pair_coeff * * :pre

			pair_style coul/streitz 12.0 ewald
			pair_style coul/streitz 12.0 wolf 0.30
			pair_coeff * * AlO.streitz Al O :pre

			pair_style tip4p/cut 1 2 7 8 0.15 12.0
			pair_coeff * * :pre

			pair_style tip4p/long 1 2 7 8 0.15 10.0
			pair_coeff * * :pre

			[Description:]

			The {coul/cut} style computes the standard Coulombic interaction
			potential given by

			:c,image(Eqs/pair_coulomb.jpg)

			where C is an energy-conversion constant, Qi and Qj are the charges on
			the 2 atoms, and epsilon is the dielectric constant which can be set
			by the "dielectric"_dielectric.html command. The cutoff Rc truncates
			the interaction distance.

			:line

			Style {coul/debye} adds an additional exp() damping factor to the
			Coulombic term, given by

			:c,image(Eqs/pair_debye.jpg)

			where kappa is the Debye length. This potential is another way to
			mimic the screening effect of a polar solvent.

			:line

			Style {coul/dsf} computes Coulombic interactions via the damped
			shifted force model described in "Fennell"_#Fennell1, given by:

			:c,image(Eqs/pair_coul_dsf.jpg)

			where {alpha} is the damping parameter and erfc() is the
			complementary error-function. The potential corrects issues in the
			Wolf model (described below) to provide consistent forces and energies
			(the Wolf potential is not differentiable at the cutoff) and smooth
			decay to zero.

			:line

			Style {coul/wolf} computes Coulombic interactions via the Wolf
			summation method, described in "Wolf"_#Wolf1, given by:

			:c,image(Eqs/pair_coul_wolf.jpg)

			where {alpha} is the damping parameter, and erc() and erfc() are
			error-function and complementary error-function terms. This potential
			is essentially a short-range, spherically-truncated,
			charge-neutralized, shifted, pairwise {1/r} summation. With a
			manipulation of adding and subtracting a self term (for i = j) to the
			first and second term on the right-hand-side, respectively, and a
			small enough {alpha} damping parameter, the second term shrinks and
			the potential becomes a rapidly-converging real-space summation. With
			a long enough cutoff and small enough alpha parameter, the energy and
			forces calculated by the Wolf summation method approach those of the
			Ewald sum. So it is a means of getting effective long-range
			interactions with a short-range potential.

			:line

			Style {coul/streitz} is the Coulomb pair interaction defined as part
			of the Streitz-Mintmire potential, as described in "this
			paper"_#Streitz2, in which charge distribution about an atom is modeled
			as a Slater 1{s} orbital. More details can be found in the referenced
			paper. To fully reproduce the published Streitz-Mintmire potential,
			which is a variable charge potential, style {coul/streitz} must be
			used with "pair_style eam/alloy"_pair_eam.html (or some other
			short-range potential that has been parameterized appropriately) via
			the "pair_style hybrid/overlay"_pair_hybrid.html command. Likewise,
			charge equilibration must be performed via the "fix
			qeq/slater"_fix_qeq.html command. For example:

			pair_style hybrid/overlay coul/streitz 12.0 wolf 0.31 eam/alloy
			pair_coeff * * coul/streitz AlO.streitz Al O
			pair_coeff * * eam/alloy AlO.eam.alloy Al O
			fix 1 all qeq/slater 1 12.0 1.0e-6 100 coul/streitz :pre

			The keyword {wolf} in the coul/streitz command denotes computing
			Coulombic interactions via Wolf summation. An additional damping
			parameter is required for the Wolf summation, as described for the
			coul/wolf potential above. Alternatively, Coulombic interactions can
			be computed via an Ewald summation. For example:

			pair_style hybrid/overlay coul/streitz 12.0 ewald eam/alloy
			kspace_style ewald 1e-6 :pre

			Keyword {ewald} does not need a damping parameter, but a
			"kspace_style"_kspace_style.html must be defined, which can be style
			{ewald} or {pppm}. The Ewald method was used in Streitz and
			Mintmire's original paper, but a Wolf summation offers a speed-up in
			some cases.

			For the fix qeq/slater command, the {qfile} can be a filename that
			contains QEq parameters as discussed on the "fix qeq"_fix_qeq.html
			command doc page. Alternatively {qfile} can be replaced by
			"coul/streitz", in which case the fix will extract QEq parameters from
			the coul/streitz pair style itself.

			See the examples/strietz directory for an example input script that
			uses the Streitz-Mintmire potential. The potentials directory has the
			AlO.eam.alloy and AlO.streitz potential files used by the example.

			Note that the Streiz-Mintmire potential is generally used for oxides,
			but there is no conceptual problem with extending it to nitrides and
			carbides (such as SiC, TiN). Pair coul/strietz used by itself or with
			any other pair style such as EAM, MEAM, Tersoff, or LJ in
			hybrid/overlay mode. To do this, you would need to provide a
			Streitz-Mintmire parameterization for the material being modeled.

			:line

			Styles {coul/long} and {coul/msm} compute the same Coulombic
			interactions as style {coul/cut} except that an additional damping
			factor is applied so it can be used in conjunction with the
			"kspace_style"_kspace_style.html command and its {ewald} or {pppm}
			option. The Coulombic cutoff specified for this style means that
			pairwise interactions within this distance are computed directly;
			interactions outside that distance are computed in reciprocal space.

			Style {coul/long/cs} is identical to {coul/long} except that a term is
			added for the "core/shell model"_Section_howto.html#howto_25 to allow
			charges on core and shell particles to be separated by r = 0.0.

			Styles {tip4p/cut} and {tip4p/long} implement the coulomb part of
			the TIP4P water model of "(Jorgensen)"_#Jorgensen3, which introduces
			a massless site located a short distance away from the oxygen atom
			along the bisector of the HOH angle. The atomic types of the oxygen and
			hydrogen atoms, the bond and angle types for OH and HOH interactions,
			and the distance to the massless charge site are specified as
			pair_style arguments. Style {tip4p/cut} uses a global cutoff for
			Coulomb interactions; style {tip4p/long} is for use with a long-range
			Coulombic solver (Ewald or PPPM).

			NOTE: For each TIP4P water molecule in your system, the atom IDs for
			the O and 2 H atoms must be consecutive, with the O atom first. This
			is to enable LAMMPS to "find" the 2 H atoms associated with each O
			atom. For example, if the atom ID of an O atom in a TIP4P water
			molecule is 500, then its 2 H atoms must have IDs 501 and 502.

			See the "howto section"_Section_howto.html#howto_8 for more
			information on how to use the TIP4P pair styles and lists of
			parameters to set. Note that the neighbor list cutoff for Coulomb
			interactions is effectively extended by a distance 2*qdist when using
			the TIP4P pair style, to account for the offset distance of the
			fictitious charges on O atoms in water molecules. Thus it is
			typically best in an efficiency sense to use a LJ cutoff >= Coulomb
			cutoff + 2*qdist, to shrink the size of the neighbor list. This leads
			to slightly larger cost for the long-range calculation, so you can
			test the trade-off for your model.

			:line

			Note that these potentials are designed to be combined with other pair
			potentials via the "pair_style hybrid/overlay"_pair_hybrid.html
			command. This is because they have no repulsive core. Hence if they
			are used by themselves, there will be no repulsion to keep two
			oppositely charged particles from moving arbitrarily close to each
			other.

			The following coefficients must be defined for each pair of atoms
			types via the "pair_coeff"_pair_coeff.html command as in the examples
			above, or in the data file or restart files read by the
			"read_data"_read_data.html or "read_restart"_read_restart.html
			commands, or by mixing as described below:

			cutoff (distance units) :ul

			For {coul/cut} and {coul/debye}, the cutoff coefficient is optional.
			If it is not used (as in some of the examples above), the default
			global value specified in the pair_style command is used.

			For {coul/long} and {coul/msm} no cutoff can be specified for an
			individual I,J type pair via the pair_coeff command. All type pairs
			use the same global Coulombic cutoff specified in the pair_style
			command.

			:line

			Styles with a {gpu}, {intel}, {kk}, {omp}, or {opt} suffix are
			functionally the same as the corresponding style without the suffix.
			They have been optimized to run faster, depending on your available
			hardware, as discussed in "Section 5"_Section_accelerate.html
			of the manual. The accelerated styles take the same arguments and
			should produce the same results, except for round-off and precision
			issues.

			These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
			USER-OMP and OPT packages, respectively. They are only enabled if
			LAMMPS was built with those packages. See the "Making
			LAMMPS"_Section_start.html#start_3 section for more info.

			You can specify the accelerated styles explicitly in your input script
			by including their suffix, or you can use the "-suffix command-line
			switch"_Section_start.html#start_6 when you invoke LAMMPS, or you can
			use the "suffix"_suffix.html command in your input script.

			See "Section 5"_Section_accelerate.html of the manual for
			more instructions on how to use the accelerated styles effectively.

			:line

			[Mixing, shift, table, tail correction, restart, rRESPA info]:

			For atom type pairs I,J and I != J, the cutoff distance for the
			{coul/cut} style can be mixed. The default mix value is {geometric}.
			See the "pair_modify" command for details.

			The "pair_modify"_pair_modify.html shift option is not relevant
			for these pair styles.

			The {coul/long} style supports the "pair_modify"_pair_modify.html
			table option for tabulation of the short-range portion of the
			long-range Coulombic interaction.

			These pair styles do not support the "pair_modify"_pair_modify.html
			tail option for adding long-range tail corrections to energy and
			pressure.

			These pair styles write their information to "binary restart
			files"_restart.html, so pair_style and pair_coeff commands do not need
			to be specified in an input script that reads a restart file.

			This pair style can only be used via the {pair} keyword of the
			"run_style respa"_run_style.html command. It does not support the
			{inner}, {middle}, {outer} keywords.

			:line

			[Restrictions:]

			The {coul/long}, {coul/msm} and {tip4p/long} styles are part of the
			KSPACE package. The {coul/long/cs} style is part of the CORESHELL
			package. They are only enabled if LAMMPS was built with that package.
			See the "Making LAMMPS"_Section_start.html#start_3 section for more info.

			[Related commands:]

			"pair_coeff"_pair_coeff.html, "pair_style,
			hybrid/overlay"_pair_hybrid.html, "kspace_style"_kspace_style.html

			[Default:] none

			:line

			:link(Wolf1)
			[(Wolf)] D. Wolf, P. Keblinski, S. R. Phillpot, J. Eggebrecht, J Chem
			Phys, 110, 8254 (1999).

			:link(Fennell1)
			[(Fennell)] C. J. Fennell, J. D. Gezelter, J Chem Phys, 124,
			234104 (2006).

			:link(Streitz2)
			[(Streitz)] F. H. Streitz, J. W. Mintmire, Phys Rev B, 50, 11996-12003
			(1994).

			:link(Jorgensen3)
			[(Jorgensen)] Jorgensen, Chandrasekhar, Madura, Impey, Klein, J Chem
			Phys, 79, 926 (1983).

lammps/doc/src/pair_coul.txt76fb4e08152fmaster

pair_coul.txtView Options

lammps/doc/src/pair_coul.txt
76fb4e08152fmaster

pair_coul.txt
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