"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 gauss command :h3 pair_style gauss/gpu command :h3 pair_style gauss/omp command :h3 pair_style gauss/cut command :h3 pair_style gauss/cut/omp command :h3 [Syntax:] pair_style gauss cutoff pair_style gauss/cut cutoff :pre cutoff = global cutoff for Gauss interactions (distance units) :ul [Examples:] pair_style gauss 12.0 pair_coeff * * 1.0 0.9 pair_coeff 1 4 1.0 0.9 10.0 :pre pair_style gauss/cut 3.5 pair_coeff 1 4 0.2805 1.45 0.112 :pre [Description:] Style {gauss} computes a tethering potential of the form :c,image(Eqs/pair_gauss.jpg) between an atom and its corresponding tether site which will typically be a frozen atom in the simulation. Rc is the cutoff. The following coefficients must be defined for each pair of atom 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: A (energy units) B (1/distance^2 units) cutoff (distance units) :ul The last coefficient is optional. If not specified, the global cutoff is used. Style {gauss/cut} computes a generalized Gaussian interaction potential between pairs of particles: :c,image(Eqs/pair_gauss_cut.jpg) where H determines together with the standard deviation sigma_h the peak height of the Gaussian function, and r_mh the peak position. Examples of the use of the Gaussian potentials include implicit solvent simulations of salt ions "(Lenart)"_#Lenart and of surfactants "(Jusufi)"_#Jusufi. In these instances the Gaussian potential mimics the hydration barrier between a pair of particles. The hydration barrier is located at r_mh and has a width of sigma_h. The prefactor determines the height of the potential barrier. The following coefficients must be defined for each pair of atom types via the "pair_coeff"_pair_coeff.html command as in the example above, or in the data file or restart files read by the "read_data"_read_data.html or "read_restart"_read_restart.html commands: H (energy * distance units) r_mh (distance units) sigma_h (distance units) cutoff (distance units) :ul The last coefficient is optional. If not specified, the global cutoff is used. :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 switch7_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 A, B, H, sigma_h, r_mh parameters, and the cutoff distance for these pair styles can be mixed: A (energy units) sqrt(1/B) (distance units, see below) H (energy units) sigma_h (distance units) r_mh (distance units) cutoff (distance units):ul The default mix value is {geometric}. Only {arithmetic} and {geometric} mix values are supported. See the "pair_modify" command for details. The A and H parameters are mixed using the same rules normally used to mix the "epsilon" parameter in a Lennard Jones interaction. The sigma_h, r_mh, and the cutoff distance are mixed using the same rules used to mix the "sigma" parameter in a Lennard Jones interaction. The B parameter is converted to a distance (sigma), before mixing (using sigma=B^-0.5), and converted back to a coefficient afterwards (using B=sigma^2). Negative A values are converted to positive A values (using abs(A)) before mixing, and converted back after mixing (by multiplying by sign(Ai)*sign(Aj)). This way, if either particle is repulsive (if Ai<0 or Aj<0), then the default interaction between both particles will be repulsive. The {gauss} style does not support the "pair_modify"_pair_modify.html shift option. There is no effect due to the Gaussian well beyond the cutoff; hence reasonable cutoffs need to be specified. The {gauss/cut} style supports the "pair_modify"_pair_modify.html shift option for the energy of the Gauss-potential portion of the pair interaction. The "pair_modify"_pair_modify.html table and tail options are not relevant for these pair styles. 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. These pair styles can only be used via the {pair} keyword of the "run_style respa"_run_style.html command. They do not support the {inner}, {middle}, {outer} keywords. The {gauss} pair style tallies an "occupancy" count of how many Gaussian-well sites have an atom within the distance at which the force is a maximum = sqrt(0.5/b). This quantity can be accessed via the "compute pair"_compute_pair.html command as a vector of values of length 1. To print this quantity to the log file (with a descriptive column heading) the following commands could be included in an input script: compute gauss all pair gauss variable occ equal c_gauss\[1\] thermo_style custom step temp epair v_occ :pre :line [Restrictions:] The {gauss/cut} style is part of the "user-misc" package. It is only enabled if LAMMPS is build with that package. See the "Making of LAMMPS"_Section_start.html#start_3 section for more info. [Related commands:] "pair_coeff"_pair_coeff.html, "pair_style coul/diel"_pair_coul_diel.html [Default:] none :link(Lenart) [(Lenart)] Lenart , Jusufi, and Panagiotopoulos, J Chem Phys, 126, 044509 (2007). :link(Jusufi) [(Jusufi)] Jusufi, Hynninen, and Panagiotopoulos, J Phys Chem B, 112, 13783 (2008).