Added pair_style lj/cubic
git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@6854 f3b2605a-c512-4ea7-a41b-209d697bcdaa
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athomps
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doc/pair_lj_cubic.html
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doc/pair_lj_cubic.html
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<HTML>
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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</CENTER>
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<HR>
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<H3>pair_style lj/cubic command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>pair_style lj/cubic
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</PRE>
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<P><B>Examples:</B>
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</P>
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<PRE>pair_style lj/cubic
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pair_coeff * * 1.0 0.8908987
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>The <I>lj/cubic</I> style computes a truncated LJ interaction potential whose
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energy and force are continuous everywhere. This is
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achieved by replacing the LJ function outside the inflection point with
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a cubic function of distance, so that both the energy and force are
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continuous at the inflection point, and go to zero at the
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cutoff distance. The LJ potential inside the inflection point is
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unchanged. The location of the inflection point rs is defined
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by the LJ diameter, rs/sigma = (26/7)^1/6. The cutoff distance
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is defined by rcut/rs = 67/48.
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</P>
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<P>This potential is commonly used to study the shock compression
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of FCC solids, as in the paper by Holian and Ravelo <A HREF = "#Holian">(Holian)</A>.
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</P>
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<P>The following coefficients must be defined for each pair of atoms
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types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the example
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above, or in the data file or restart files read by the
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<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
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commands, or by mixing as described below:
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</P>
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<UL><LI>epsilon (energy units)
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<LI>sigma (distance units)
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</UL>
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<P>Note that sigma is defined in the LJ formula as the zero-crossing
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distance for the potential, not as the energy minimum, which
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is located at 2^(1/6)*sigma. In the above example, sigma = 0.8908987,
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so the energy minimum is located at r = 1.
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</P>
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<HR>
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<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
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</P>
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<P>For atom type pairs I,J and I != J, the epsilon and sigma coefficients
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and cutoff distance for all of the lj/cut pair styles can be mixed.
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The default mix value is <I>geometric</I>. See the "pair_modify" command
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for details.
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</P>
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<P>The lj/cubic pair style does not support the
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<A HREF = "pair_modify.html">pair_modify</A> shift option,
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since pair interaction is already smoothed to 0.0 at the
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cutoff.
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</P>
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<P>The <A HREF = "pair_modify.html">pair_modify</A> table option is not relevant
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for this pair style.
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</P>
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<P>The lj/cubic pair style does not support the
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<A HREF = "pair_modify.html">pair_modify</A> tail option for adding long-range tail
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corrections to energy and pressure, since there are no corrections for
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a potential that goes to 0.0 at the cutoff.
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</P>
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<P>The lj/cubic pair style writes its information to <A HREF = "restart.html">binary
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restart files</A>, so pair_style and pair_coeff commands do
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not need to be specified in an input script that reads a restart file.
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</P>
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<P>The lj/cubic pair style can only be used via the <I>pair</I>
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keyword of the <A HREF = "run_style.html">run_style respa</A> command. It does not
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support the <I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
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</P>
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<HR>
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "pair_coeff.html">pair_coeff</A>
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</P>
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<P><B>Default:</B> none
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</P>
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<HR>
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<A NAME = "Holian"></A>
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<P><B>(Holian)</B> Holian and Ravelo, Phys Rev B, 51, 11275 (1995).
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</P>
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</HTML>
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92
doc/pair_lj_cubic.txt
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92
doc/pair_lj_cubic.txt
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"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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pair_style lj/cubic command :h3
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[Syntax:]
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pair_style lj/cubic :pre
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[Examples:]
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pair_style lj/cubic
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pair_coeff * * 1.0 0.8908987 :pre
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[Description:]
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The {lj/cubic} style computes a truncated LJ interaction potential whose
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energy and force are continuous everywhere. This is
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achieved by replacing the LJ function outside the inflection point with
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a cubic function of distance, so that both the energy and force are
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continuous at the inflection point, and go to zero at the
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cutoff distance. The LJ potential inside the inflection point is
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unchanged. The location of the inflection point rs is defined
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by the LJ diameter, rs/sigma = (26/7)^1/6. The cutoff distance
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is defined by rcut/rs = 67/48.
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This potential is commonly used to study the shock compression
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of FCC solids, as in the paper by Holian and Ravelo "(Holian)"_#Holian.
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The following coefficients must be defined for each pair of atoms
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types via the "pair_coeff"_pair_coeff.html command as in the example
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above, or in the data file or restart files read by the
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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands, or by mixing as described below:
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epsilon (energy units)
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sigma (distance units) :ul
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Note that sigma is defined in the LJ formula as the zero-crossing
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distance for the potential, not as the energy minimum, which
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is located at 2^(1/6)*sigma. In the above example, sigma = 0.8908987,
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so the energy minimum is located at r = 1.
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:line
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[Mixing, shift, table, tail correction, restart, rRESPA info]:
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For atom type pairs I,J and I != J, the epsilon and sigma coefficients
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and cutoff distance for all of the lj/cut pair styles can be mixed.
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The default mix value is {geometric}. See the "pair_modify" command
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for details.
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The lj/cubic pair style does not support the
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"pair_modify"_pair_modify.html shift option,
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since pair interaction is already smoothed to 0.0 at the
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cutoff.
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The "pair_modify"_pair_modify.html table option is not relevant
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for this pair style.
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The lj/cubic pair style does not support the
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"pair_modify"_pair_modify.html tail option for adding long-range tail
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corrections to energy and pressure, since there are no corrections for
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a potential that goes to 0.0 at the cutoff.
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The lj/cubic pair style writes its information to "binary
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restart files"_restart.html, so pair_style and pair_coeff commands do
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not need to be specified in an input script that reads a restart file.
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The lj/cubic pair style can only be used via the {pair}
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keyword of the "run_style respa"_run_style.html command. It does not
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support the {inner}, {middle}, {outer} keywords.
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:line
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[Restrictions:] none
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[Related commands:]
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"pair_coeff"_pair_coeff.html
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[Default:] none
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:line
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:link(Holian)
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[(Holian)] Holian and Ravelo, Phys Rev B, 51, 11275 (1995).
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