From 7e1e28af0ea39b4ac1eb7b7625dfbe64bc9d25b1 Mon Sep 17 00:00:00 2001 From: sjplimp Date: Fri, 20 Apr 2007 15:38:14 +0000 Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@503 f3b2605a-c512-4ea7-a41b-209d697bcdaa --- doc/Section_commands.html | 12 +++---- doc/Section_commands.txt | 1 + doc/fix_heat.html | 69 +++++++++++++++++++++++++++++++++++++++ doc/fix_heat.txt | 65 ++++++++++++++++++++++++++++++++++++ 4 files changed, 141 insertions(+), 6 deletions(-) create mode 100644 doc/fix_heat.html create mode 100644 doc/fix_heat.txt diff --git a/doc/Section_commands.html b/doc/Section_commands.html index 2324950257..1bf90be475 100644 --- a/doc/Section_commands.html +++ b/doc/Section_commands.html @@ -318,12 +318,12 @@ description:

- - - - - - + + + + +
addforceaveforceave/spatialave/timebox/relaxcomdeformdeposit
dragefieldenforce2dfreezegran/diaggravitygyrationindent
langevinlineforcemsdmomentumnphnptnvenve/asphere
nve/grannve/noforcenvtorient/fccplaneforcepoemspourprint
rdfrecenterrigidsetforceshakespringspring/rgspring/self
temp/rescaletmduniaxialviscousvolume/rescalewall/granwall/lj93wall/lj126
wall/reflectwiggle +
dragefieldenforce2dfreezegran/diaggravitygyrationheat
indentlangevinlineforcemsdmomentumnphnptnve
nve/aspherenve/grannve/noforcenvtorient/fccplaneforcepoemspour
printrdfrecenterrigidsetforceshakespringspring/rg
spring/selftemp/rescaletmduniaxialviscousvolume/rescalewall/granwall/lj93
wall/lj126wall/reflectwiggle
diff --git a/doc/Section_commands.txt b/doc/Section_commands.txt index c6820f8012..a79cd76867 100644 --- a/doc/Section_commands.txt +++ b/doc/Section_commands.txt @@ -386,6 +386,7 @@ description: "gran/diag"_fix_gran_diag.html, "gravity"_fix_gravity.html, "gyration"_fix_gyration.html, +"heat"_fix_heat.html, "indent"_fix_indent.html, "langevin"_fix_langevin.html, "lineforce"_fix_lineforce.html, diff --git a/doc/fix_heat.html b/doc/fix_heat.html new file mode 100644 index 0000000000..abed35a11f --- /dev/null +++ b/doc/fix_heat.html @@ -0,0 +1,69 @@ + +
LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Commands +
+ + + + + + +
+ +

fix heat command +

+

Syntax: +

+
fix ID group-ID heat N eflux 
+
+ +

Examples: +

+
fix 3 qin heat 1 1.0
+fix 4 qout heat 1 -1.0 
+
+

Description: +

+

Add non-translational kinetic energy (heat) to the a group of atoms +such that their aggregate momentum is conserved. Two of these fixes +can be used to establish a temperature gradient across a simulation +domain by adding heat to one group of atoms (hot reservoir) and +subracting heat from another (cold reservoir). I.e. a McDLT +simulation. Note that the fix is applied to a group of atoms not a +geometric region, so that the atoms are affected wherever they may +move to. +

+

Heat addition/subtraction is performed every N timesteps. The eflux +parameter determines the change in aggregate energy of the entire +group of atoms. If heat is subtracted from the system too +aggressively so that the group's kinetic energy goes to zero, LAMMPS +halts with an error message. +

+

Fix heat is different from a thermostat such as fix nvt +or fix temp/rescale in that energy is +added/subtracted continually. Thus if there isn't another mechanism +in place to counterbalance this effect, the entire system will heat or +cool continously. You can use multiple heat fixes so that the net +energy change is 0.0 or use fix viscous to drain energy +from the system. +

+

This fix does not change the coordinates of its atoms; it only scales +their velocities. Thus you must still use an integration fix +(e.g. fix nve) on the affected atoms. This fix should +not normally be used on atoms that have their temperature controlled +by another fix - e.g. fix nvt or fix +langevin fix. +

+

Restrictions: none +

+

Related commands: +

+

compute temp, compute +temp/region +

+

Default: none +

+ diff --git a/doc/fix_heat.txt b/doc/fix_heat.txt new file mode 100644 index 0000000000..691aa4d4a6 --- /dev/null +++ b/doc/fix_heat.txt @@ -0,0 +1,65 @@ +"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 + +fix heat command :h3 + +[Syntax:] + +fix ID group-ID heat N eflux :pre + +ID, group-ID are documented in "fix"_fix.html command +heat = style name of this fix command +N = add/subtract heat every this many timesteps +eflux = rate of heat addition or subtraction (energy/time units) :ul + +[Examples:] + +fix 3 qin heat 1 1.0 +fix 4 qout heat 1 -1.0 :pre + +[Description:] + +Add non-translational kinetic energy (heat) to the a group of atoms +such that their aggregate momentum is conserved. Two of these fixes +can be used to establish a temperature gradient across a simulation +domain by adding heat to one group of atoms (hot reservoir) and +subracting heat from another (cold reservoir). I.e. a McDLT +simulation. Note that the fix is applied to a group of atoms not a +geometric region, so that the atoms are affected wherever they may +move to. + +Heat addition/subtraction is performed every N timesteps. The {eflux} +parameter determines the change in aggregate energy of the entire +group of atoms. If heat is subtracted from the system too +aggressively so that the group's kinetic energy goes to zero, LAMMPS +halts with an error message. + +Fix heat is different from a thermostat such as "fix nvt"_fix_nvt.html +or "fix temp/rescale"_fix_temp_rescale.html in that energy is +added/subtracted continually. Thus if there isn't another mechanism +in place to counterbalance this effect, the entire system will heat or +cool continously. You can use multiple heat fixes so that the net +energy change is 0.0 or use "fix viscous"_fix_viscous to drain energy +from the system. + +This fix does not change the coordinates of its atoms; it only scales +their velocities. Thus you must still use an integration fix +(e.g. "fix nve"_fix_nve.html) on the affected atoms. This fix should +not normally be used on atoms that have their temperature controlled +by another fix - e.g. "fix nvt"_fix_nvt.html or "fix +langevin"_fix_langevin.html fix. + +[Restrictions:] none + +[Related commands:] + +"compute temp"_compute_temp.html, "compute +temp/region"_compute_temp_region.html + +[Default:] none +