git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@5811 f3b2605a-c512-4ea7-a41b-209d697bcdaa

doc/fix_box_relax.html

@@ -82,6 +82,19 @@ re-scaled.  This can be useful for leaving the coordinates of atoms in
 a solid substrate unchanged and controlling the pressure of a
 surrounding fluid.
 </P>
+<P>IMPORTANT NOTE: Appling an external pressure to tilt dimensions <I>xy</I>,
+<I>xz</I>, <I>yz</I> can sometimes result in arbitrarily large values of the
+tilt dimensions, i.e. a dramatically deformed simulation box.  This
+typically indicates that there is something badly wrong with how the
+simulation was constructed.  The two most common sources of this error
+are applying a shear stress to a liquid system or specifying an
+external shear stress tensor that exceeds the yield stress of the
+solid.  In either case the minimization is either not going to
+converge at all, or converge to a bogus conformation.  Note that
+LAMMPS will not throw an error when the tilt value becomes extreme,
+but the final box may be unsuitable for running dynamics on, unless
+fix deform is used first to remap the box to a valid tilt value.
+</P>
 <HR>
 
 <P>The <I>couple</I> keyword allows two or three of the diagonal components of

doc/fix_box_relax.txt

@@ -76,6 +76,19 @@ re-scaled.  This can be useful for leaving the coordinates of atoms in
 a solid substrate unchanged and controlling the pressure of a
 surrounding fluid.
 
+IMPORTANT NOTE: Appling an external pressure to tilt dimensions {xy},
+{xz}, {yz} can sometimes result in arbitrarily large values of the
+tilt dimensions, i.e. a dramatically deformed simulation box.  This
+typically indicates that there is something badly wrong with how the
+simulation was constructed.  The two most common sources of this error
+are applying a shear stress to a liquid system or specifying an
+external shear stress tensor that exceeds the yield stress of the
+solid.  In either case the minimization is either not going to
+converge at all, or converge to a bogus conformation.  Note that
+LAMMPS will not throw an error when the tilt value becomes extreme,
+but the final box may be unsuitable for running dynamics on, unless
+fix deform is used first to remap the box to a valid tilt value.
+
 :line
 
 The {couple} keyword allows two or three of the diagonal components of