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. +
The couple keyword allows two or three of the diagonal components of diff --git a/doc/fix_box_relax.txt b/doc/fix_box_relax.txt index 606cb3edab..510458504c 100644 --- a/doc/fix_box_relax.txt +++ b/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