.. index:: pair_style morse pair_style morse command ======================== pair_style morse/cuda command ============================= pair_style morse/gpu command ============================ pair_style morse/omp command ============================ pair_style morse/opt command ============================ pair_style morse/smooth/linear command ====================================== pair_style morse/smooth/linear/omp command ========================================== Syntax """""" .. parsed-literal:: pair_style morse cutoff * cutoff = global cutoff for Morse interactions (distance units) Examples """""""" .. parsed-literal:: pair_style morse 2.5 pair_style morse/smooth/linear 2.5 pair_coeff * * 100.0 2.0 1.5 pair_coeff 1 1 100.0 2.0 1.5 3.0 Description """"""""""" Style *morse* computes pairwise interactions with the formula .. image:: Eqs/pair_morse.jpg :align: center Rc is the cutoff. The following coefficients must be defined for each pair of atoms 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: * D0 (energy units) * alpha (1/distance units) * r0 (distance units) * cutoff (distance units) * The last coefficient is optional. If not specified, the global morse * cutoff is used. ---------- The *smooth/linear* variant is similar to the lj/smooth/linear variant in that it adds to the potential a shift and a linear term to make both the potential energy and force go to zero at the cut-off: .. image:: Eqs/pair_morse_smooth_linear.jpg :align: center The syntax of the pair_style and pair_coeff commands are the same for the *morse* and *morse/smooth/linear* styles. ---------- 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 :ref:`-suffix command-line switch ` 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**\ : None of these pair styles support mixing. Thus, coefficients for all I,J pairs must be specified explicitly. All of these pair styles support the :doc:`pair_modify ` shift option for the energy of the pair interaction. The :doc:`pair_modify ` table options is not relevant for the Morse pair styles. None of these pair styles support the :doc:`pair_modify ` tail option for adding long-range tail corrections to energy and pressure. All of 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. ---------- Restrictions """""""""""" The *morse/smooth/linear* pair style is only enabled if LAMMPS was built with the USER-MISC package. See the :ref:`Making LAMMPS ` section for more info. Related commands """""""""""""""" :doc:`pair_coeff ` **Default:** none .. _lws: http://lammps.sandia.gov .. _ld: Manual.html .. _lc: Section_commands.html#comm