diff --git a/doc/src/fix_npt_cauchy.rst b/doc/src/fix_npt_cauchy.rst index 480e2e5314..672c1c6723 100644 --- a/doc/src/fix_npt_cauchy.rst +++ b/doc/src/fix_npt_cauchy.rst @@ -13,7 +13,7 @@ Syntax * ID, group-ID are documented in :doc:`fix ` command * style_name = *npt/cauchy* * one or more keyword/value pairs may be appended -* keyword = *temp* or *iso* or *aniso* or *tri* or *x* or *y* or *z* or *xy* or *yz* or *xz* or *couple* or *tchain* or *pchain* or *mtk* or *tloop* or *ploop* or *nreset* or *drag* or *dilate* or *scalexy* or *scaleyz* or *scalexz* or *flip* or *fixedpoint* or *update* +* keyword = *temp* or *iso* or *aniso* or *tri* or *x* or *y* or *z* or *xy* or *yz* or *xz* or *couple* or *tchain* or *pchain* or *mtk* or *tloop* or *ploop* or *nreset* or *drag* or *dilate* or *scalexy* or *scaleyz* or *scalexz* or *flip* or *fixedpoint* .. parsed-literal:: @@ -45,9 +45,8 @@ Syntax *scaleyz* value = *yes* or *no* = scale yz with lz *scalexz* value = *yes* or *no* = scale xz with lz *flip* value = *yes* or *no* = allow or disallow box flips when it becomes highly skewed - *cauchystat* cauchystat values = alpha continue - alpha = strength of Cauchy stress control parameter - continue = *yes* or *no* = whether of not to continue from a previous run + *alpha* value = strength of Cauchy stress control parameter + *continue* value = *yes* or *no* = whether of not to continue from a previous run *fixedpoint* values = x y z x,y,z = perform barostat dilation/contraction around this point (distance units) @@ -56,7 +55,7 @@ Examples .. code-block:: LAMMPS - fix 1 water npt/cauchy temp 300.0 300.0 100.0 iso 0.0 0.0 1000.0 + fix 1 water npt/cauchy temp 300.0 300.0 100.0 iso 0.0 0.0 1000.0 alpha 0.001 Description """"""""""" @@ -573,14 +572,7 @@ can only be used if the second dimension in the keyword is periodic, and if the tilt factor is not coupled to the barostat via keywords *tri*\ , *yz*\ , *xz*\ , and *xy*\ . -Without the *cauchystat* keyword, the barostat algorithm -controls the Second-Piola Kirchhoff stress, which is a stress measure -referred to the unmodified (initial) simulation box. If the box -deforms substantially during the equilibration, the difference between -the set values and the final true (Cauchy) stresses can be -considerable. - -The *cauchystat* keyword modifies the barostat as per Miller et +The *alpha* keyword modifies the barostat as per Miller et al. (Miller)_"#nc-Miller" so that the Cauchy stress is controlled. *alpha* is the non-dimensional parameter, typically set to 0.001 or 0.01 that determines how aggressively the algorithm drives the system @@ -598,13 +590,12 @@ sequence over several fixes. Setting *alpha* to zero is not permitted. To "turn off" the cauchystat control and thus restore the equilibrium stress -fluctuations, two subsequent fixes should be used. In the first, the -cauchystat flag is used and the simulation box equilibrates to the -correct shape for the desired stresses. In the second, the *fix* -statement is identical except that the *cauchystat* keyword is removed -(along with related *alpha* and *continue* values). This restores the -original Parrinello-Rahman algorithm, but now with the correct simulation -box shape from the first fix. +fluctuations, two subsequent fixes should be used. In the first, fix +npt/cauchy is used and the simulation box equilibrates to the +correct shape for the desired stresses. In the second, +:doc:`fix npt ` is used instead which uses the +original Parrinello-Rahman algorithm, but now with the corrected +simulation box shape from using fix npt/cauchy. This fix can be used with dynamic groups as defined by the :doc:`group ` command. Likewise it can be used with groups to