pair_style meam/sw/spline ========================= pair_style meam/sw/spline/omp ============================= Syntax """""" .. parsed-literal:: pair_style meam/sw/spline Examples """""""" .. parsed-literal:: pair_style meam/sw/spline pair_coeff * * Ti.meam.sw.spline Ti pair_coeff * * Ti.meam.sw.spline Ti Ti Ti Description """"""""""" The *meam/sw/spline* style computes pairwise interactions for metals using a variant of modified embedded-atom method (MEAM) potentials :ref:`(Lenosky) ` with an additional Stillinger-Weber (SW) term :ref:`(Stillinger) ` in the energy. This form of the potential was first proposed by Nicklas, Fellinger, and Park :ref:`(Nicklas) `. We refer to it as MEAM+SW. The total energy E is given by .. image:: Eqs/pair_meam_sw_spline.jpg :align: center where rho_I is the density at atom I, theta_JIK is the angle between atoms J, I, and K centered on atom I. The seven functions Phi, F, G, U, rho, f, and g are represented by cubic splines. The cutoffs and the coefficients for these spline functions are listed in a parameter file which is specified by the :doc:`pair_coeff ` command. Parameter files for different elements are included in the "potentials" directory of the LAMMPS distribution and have a ".meam.sw.spline" file suffix. All of these files are parameterized in terms of LAMMPS :doc:`metal units `. Note that unlike for other potentials, cutoffs for spline-based MEAM+SW potentials are not set in the pair_style or pair_coeff command; they are specified in the potential files themselves. Unlike the EAM pair style, which retrieves the atomic mass from the potential file, the spline-based MEAM+SW potentials do not include mass information; thus you need to use the :doc:`mass ` command to specify it. Only a single pair_coeff command is used with the meam/sw/spline style which specifies a potential file with parameters for all needed elements. These are mapped to LAMMPS atom types by specifying N additional arguments after the filename in the pair_coeff command, where N is the number of LAMMPS atom types: * filename * N element names = mapping of spline-based MEAM+SW elements to atom types See the :doc:`pair_coeff ` doc page for alternate ways to specify the path for the potential file. As an example, imagine the Ti.meam.sw.spline file has values for Ti. If your LAMMPS simulation has 3 atoms types and they are all to be treated with this potential, you would use the following pair_coeff command: pair_coeff * * Ti.meam.sw.spline Ti Ti Ti The 1st 2 arguments must be * * so as to span all LAMMPS atom types. The three Ti arguments map LAMMPS atom types 1,2,3 to the Ti element in the potential file. If a mapping value is specified as NULL, the mapping is not performed. This can be used when a *meam/sw/spline* potential is used as part of the hybrid pair style. The NULL values are placeholders for atom types that will be used with other potentials. .. note:: The *meam/sw/spline* style currently supports only single-element MEAM+SW potentials. It may be extended for alloy systems in the future. Example input scripts that use this pair style are provided in the examples/USER/misc/meam_sw_spline directory. ---------- **Mixing, shift, table, tail correction, restart, rRESPA info**\ : The pair style does not support multiple element types or mixing. It has been designed for pure elements only. This pair style does not support the :doc:`pair_modify ` shift, table, and tail options. The *meam/sw/spline* pair style does not write its information to :doc:`binary restart files `, since it is stored in an external potential parameter file. Thus, you need to re-specify the pair_style and pair_coeff commands in an input script that reads a restart file. The *meam/sw/spline* pair style 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 """""""""""" This pair style requires the :doc:`newton ` setting to be "on" for pair interactions. This 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 `, :doc:`pair_style meam `, :doc:`pair_style meam/spline ` **Default:** none ---------- .. _Lenosky: **(Lenosky)** Lenosky, Sadigh, Alonso, Bulatov, de la Rubia, Kim, Voter, Kress, Modell. Simul. Mater. Sci. Eng. 8, 825 (2000). .. _Stillinger: **(Stillinger)** Stillinger, Weber, Phys. Rev. B 31, 5262 (1985). .. _Nicklas: **(Nicklas)** The spline-based MEAM+SW format was first devised and used to develop potentials for bcc transition metals by Jeremy Nicklas, Michael Fellinger, and Hyoungki Park at The Ohio State University. .. _lws: http://lammps.sandia.gov .. _ld: Manual.html .. _lc: Section_commands.html#comm