From 5e2892aaccefa4ce367f01364dd0d6c1257bea55 Mon Sep 17 00:00:00 2001 From: athomps Date: Mon, 29 Aug 2011 18:44:24 +0000 Subject: [PATCH] Added pair_style lj/cubic git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@6854 f3b2605a-c512-4ea7-a41b-209d697bcdaa --- doc/pair_lj_cubic.html | 98 ++++++++++++++++++++++++++++++++++++++++++ doc/pair_lj_cubic.txt | 92 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 190 insertions(+) create mode 100644 doc/pair_lj_cubic.html create mode 100644 doc/pair_lj_cubic.txt diff --git a/doc/pair_lj_cubic.html b/doc/pair_lj_cubic.html new file mode 100644 index 0000000000..2fb0464c19 --- /dev/null +++ b/doc/pair_lj_cubic.html @@ -0,0 +1,98 @@ + +
LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Commands +
+ + + + + + +
+ +

pair_style lj/cubic command +

+

Syntax: +

+
pair_style lj/cubic 
+
+

Examples: +

+
pair_style lj/cubic
+pair_coeff * * 1.0 0.8908987 
+
+

Description: +

+

The lj/cubic style computes a truncated LJ interaction potential whose +energy and force are continuous everywhere. This is +achieved by replacing the LJ function outside the inflection point with +a cubic function of distance, so that both the energy and force are +continuous at the inflection point, and go to zero at the +cutoff distance. The LJ potential inside the inflection point is +unchanged. The location of the inflection point rs is defined +by the LJ diameter, rs/sigma = (26/7)^1/6. The cutoff distance +is defined by rcut/rs = 67/48. +

+

This potential is commonly used to study the shock compression +of FCC solids, as in the paper by Holian and Ravelo (Holian). +

+

The following coefficients must be defined for each pair of atoms +types via the pair_coeff command as in the example +above, or in the data file or restart files read by the +read_data or read_restart +commands, or by mixing as described below: +

+ +

Note that sigma is defined in the LJ formula as the zero-crossing +distance for the potential, not as the energy minimum, which +is located at 2^(1/6)*sigma. In the above example, sigma = 0.8908987, +so the energy minimum is located at r = 1. +

+
+ +

Mixing, shift, table, tail correction, restart, rRESPA info: +

+

For atom type pairs I,J and I != J, the epsilon and sigma coefficients +and cutoff distance for all of the lj/cut pair styles can be mixed. +The default mix value is geometric. See the "pair_modify" command +for details. +

+

The lj/cubic pair style does not support the +pair_modify shift option, +since pair interaction is already smoothed to 0.0 at the +cutoff. +

+

The pair_modify table option is not relevant +for this pair style. +

+

The lj/cubic pair style does not support the +pair_modify tail option for adding long-range tail +corrections to energy and pressure, since there are no corrections for +a potential that goes to 0.0 at the cutoff. +

+

The lj/cubic pair style writes its information to 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. +

+

The lj/cubic pair style can only be used via the pair +keyword of the run_style respa command. It does not +support the inner, middle, outer keywords. +

+
+ +

Restrictions: none +

+

Related commands: +

+

pair_coeff +

+

Default: none +

+
+ + + +

(Holian) Holian and Ravelo, Phys Rev B, 51, 11275 (1995). +

+ diff --git a/doc/pair_lj_cubic.txt b/doc/pair_lj_cubic.txt new file mode 100644 index 0000000000..f0a864c609 --- /dev/null +++ b/doc/pair_lj_cubic.txt @@ -0,0 +1,92 @@ +"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 lj/cubic command :h3 + +[Syntax:] + +pair_style lj/cubic :pre + +[Examples:] + +pair_style lj/cubic +pair_coeff * * 1.0 0.8908987 :pre + +[Description:] + +The {lj/cubic} style computes a truncated LJ interaction potential whose +energy and force are continuous everywhere. This is +achieved by replacing the LJ function outside the inflection point with +a cubic function of distance, so that both the energy and force are +continuous at the inflection point, and go to zero at the +cutoff distance. The LJ potential inside the inflection point is +unchanged. The location of the inflection point rs is defined +by the LJ diameter, rs/sigma = (26/7)^1/6. The cutoff distance +is defined by rcut/rs = 67/48. + +This potential is commonly used to study the shock compression +of FCC solids, as in the paper by Holian and Ravelo "(Holian)"_#Holian. + +The following coefficients must be defined for each pair of atoms +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, or by mixing as described below: + +epsilon (energy units) +sigma (distance units) :ul + +Note that sigma is defined in the LJ formula as the zero-crossing +distance for the potential, not as the energy minimum, which +is located at 2^(1/6)*sigma. In the above example, sigma = 0.8908987, +so the energy minimum is located at r = 1. + +:line + +[Mixing, shift, table, tail correction, restart, rRESPA info]: + +For atom type pairs I,J and I != J, the epsilon and sigma coefficients +and cutoff distance for all of the lj/cut pair styles can be mixed. +The default mix value is {geometric}. See the "pair_modify" command +for details. + +The lj/cubic pair style does not support the +"pair_modify"_pair_modify.html shift option, +since pair interaction is already smoothed to 0.0 at the +cutoff. + +The "pair_modify"_pair_modify.html table option is not relevant +for this pair style. + +The lj/cubic pair style does not support the +"pair_modify"_pair_modify.html tail option for adding long-range tail +corrections to energy and pressure, since there are no corrections for +a potential that goes to 0.0 at the cutoff. + +The lj/cubic pair style writes its 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. + +The lj/cubic pair style can only be used via the {pair} +keyword of the "run_style respa"_run_style.html command. It does not +support the {inner}, {middle}, {outer} keywords. + +:line + +[Restrictions:] none + +[Related commands:] + +"pair_coeff"_pair_coeff.html + +[Default:] none + +:line + +:link(Holian) +[(Holian)] Holian and Ravelo, Phys Rev B, 51, 11275 (1995).