.. index:: pair_style gauss pair_style gauss command ======================== pair_style gauss/gpu command ============================ pair_style gauss/omp command ============================ pair_style gauss/cut command ============================ pair_style gauss/cut/omp command ================================ Syntax """""" .. parsed-literal:: pair_style gauss cutoff pair_style gauss/cut cutoff * cutoff = global cutoff for Gauss interactions (distance units) Examples """""""" .. parsed-literal:: pair_style gauss 12.0 pair_coeff * * 1.0 0.9 pair_coeff 1 4 1.0 0.9 10.0 .. parsed-literal:: pair_style gauss/cut 3.5 pair_coeff 1 4 0.2805 1.45 0.112 Description """"""""""" Style *gauss* computes a tethering potential of the form .. image:: Eqs/pair_gauss.jpg :align: center 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 :doc:`pair_coeff ` command as in the examples above, or in the data file or restart files read by the :doc:`read_data ` or :doc:`read_restart ` commands: * A (energy units) * B (1/distance^2 units) * cutoff (distance units) 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: .. image:: Eqs/pair_gauss_cut.jpg :align: center 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 :ref:`(Lenart) ` and of surfactants :ref:`(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 hight of the potential barrier. The following coefficients must be defined for each pair of atom types via the :doc:`pair_coeff ` command as in the example above, or in the data file or restart files read by the :doc:`read_data ` or :doc:`read_restart ` commands: * H (energy * distance units) * r_mh (distance units) * sigma_h (distance units) The global cutoff (r_c) specified in the pair_style command is used. ---------- Styles with a *cuda*\ , *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 :doc:`Section_accelerate ` 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 USER-CUDA, GPU, USER-INTEL, KOKKOS, USER-OMP and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the :ref:`Making LAMMPS ` 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 :doc:`suffix ` command in your input script. See :doc:`Section_accelerate ` of the manual for more instructions on how to use the accelerated styles effectively. ---------- **Mixing, shift, table, tail correction, restart, rRESPA info**\ : These pair styles do not support mixing. Thus, coefficients for all I,J pairs must be specified explicitly. The *gauss* style does not support the :doc:`pair_modify ` 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 :doc:`pair_modify ` shift option for the energy of the Gauss-potential portion of the pair interaction. The :doc:`pair_modify ` table and tail options are not relevant for these pair styles. These pair styles write their information to :doc:`binary restart files `, 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 :doc:`run_style respa ` 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 :doc:`compute pair ` 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: .. parsed-literal:: compute gauss all pair gauss variable occ equal c_gauss[1] thermo_style custom step temp epair v_occ ---------- 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 :ref:`Making of LAMMPS <3>` section for more info. Related commands """""""""""""""" :doc:`pair_coeff `, :doc:`pair_style coul/diel ` **Default:** none .. _Lenart: **(Lenart)** Lenart , Jusufi, and Panagiotopoulos, J Chem Phys, 126, 044509 (2007). .. _Jusufi: **(Jusufi)** Jusufi, Hynninen, and Panagiotopoulos, J Phys Chem B, 112, 13783 (2008). .. _lws: http://lammps.sandia.gov .. _ld: Manual.html .. _lc: Section_commands.html#comm