Merge branch release-2019 into release-2020

[alexxy/gromacs.git] / docs / user-guide / mdp-options.rst

diff --git a/docs/user-guide/mdp-options.rst b/docs/user-guide/mdp-options.rst
index 35d391bffa722c1376324991f845e29d4131706e..b9901f7b70b1eb1c670721119422b0759ce157bd 100644 (file)
--- a/docs/user-guide/mdp-options.rst
+++ b/docs/user-guide/mdp-options.rst
@@ -1672,10 +1672,13 @@ pull-coord2-vec, pull-coord2-k, and so on.
 
    .. mdp-value:: direction-periodic
 
-      As :mdp-value:`pull-coord1-geometry=direction`, but allows the distance to be larger
-      than half the box size. With this geometry the box should not be
+      As :mdp-value:`pull-coord1-geometry=direction`, but does not apply
+      periodic box vector corrections to keep the distance within half
+      the box length. This is (only) useful for pushing groups apart
+      by more than half the box length by continuously changing the reference
+      location using a pull rate. With this geometry the box should not be
       dynamic (*e.g.* no pressure scaling) in the pull dimensions and
-      the pull force is not added to virial.
+      the pull force is not added to the virial.
 
    .. mdp-value:: direction-relative