From bf962e01eed60ecf317d4411c45bec587e80b260 Mon Sep 17 00:00:00 2001 From: sjplimp Date: Tue, 4 Oct 2011 15:13:00 +0000 Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@7027 f3b2605a-c512-4ea7-a41b-209d697bcdaa --- doc/fix_spring.html | 11 +++++++++++ doc/fix_spring.txt | 11 +++++++++++ 2 files changed, 22 insertions(+) diff --git a/doc/fix_spring.html b/doc/fix_spring.html index 542c3f82b6..8830056177 100644 --- a/doc/fix_spring.html +++ b/doc/fix_spring.html @@ -91,6 +91,17 @@ below the z = 0 center plane of the pore (umbrella sampling). The last example holds the ion a distance 5 away from the pore axis (assuming the center-of-mass of the pore in x,y is the pore axis).

+

IMPORTANT NOTE: The center of mass of a group of atoms is calculated +in "unwrapped" coordinates using atom image flags, which means that +the group can straddle a periodic boundary. See the dump +doc page for a discussion of unwrapped coordinates. It also means +that a spring connecting two groups or a group and the tether point +can cross a periodic boundary and its length be calculated correctly. +One exception is for rigid bodies, which should not be used with the +fix spring command, if the rigid body will cross a periodic boundary. +This is because image flags for rigid bodies are used in a different +way, as explained on the fix rigid doc page. +

Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart diff --git a/doc/fix_spring.txt b/doc/fix_spring.txt index d3e8ee3d4f..9b65065714 100644 --- a/doc/fix_spring.txt +++ b/doc/fix_spring.txt @@ -84,6 +84,17 @@ below the z = 0 center plane of the pore (umbrella sampling). The last example holds the ion a distance 5 away from the pore axis (assuming the center-of-mass of the pore in x,y is the pore axis). +IMPORTANT NOTE: The center of mass of a group of atoms is calculated +in "unwrapped" coordinates using atom image flags, which means that +the group can straddle a periodic boundary. See the "dump"_dump.html +doc page for a discussion of unwrapped coordinates. It also means +that a spring connecting two groups or a group and the tether point +can cross a periodic boundary and its length be calculated correctly. +One exception is for rigid bodies, which should not be used with the +fix spring command, if the rigid body will cross a periodic boundary. +This is because image flags for rigid bodies are used in a different +way, as explained on the "fix rigid"_doc/fix_rigid.html doc page. + [Restart, fix_modify, output, run start/stop, minimize info:] No information about this fix is written to "binary restart