cross ref fix deform and new fix nvt/uef

doc/src/fix_deform.txt

@@ -86,11 +86,16 @@ Change the volume and/or shape of the simulation box during a dynamics
 run.  Orthogonal simulation boxes have 3 adjustable parameters
 (x,y,z).  Triclinic (non-orthogonal) simulation boxes have 6
 adjustable parameters (x,y,z,xy,xz,yz).  Any or all of them can be
-adjusted independently and simultaneously by this command.  This fix
-can be used to perform non-equilibrium MD (NEMD) simulations of a
-continuously strained system.  See the "fix
+adjusted independently and simultaneously by this command.  
+
+This fix can be used to perform non-equilibrium MD (NEMD) simulations
+of a continuously strained system.  See the "fix
 nvt/sllod"_fix_nvt_sllod.html and "compute
-temp/deform"_compute_temp_deform.html commands for more details.
+temp/deform"_compute_temp_deform.html commands for more details.  Note
+that simulation of a continuously extended (extensional flow) system
+can be modeled using the "USER-UEF
+package"_Section_packages.html#USER-UEF and its "fix
+commands"_fix_nh_uef.html.
 
 For the {x}, {y}, {z} parameters, the associated dimension cannot be
 shrink-wrapped.  For the {xy}, {yz}, {xz} parameters, the associated

doc/src/fix_nh_uef.txt

@@ -36,18 +36,23 @@ fix biax_npt all npt/uef temp 400 400 100 erate -0.00001 0.000005 x 1 1 3000 :pr
 
 [Description:]
 
-This fix is used to simulate non-equilibrium molecular dynamics (NEMD)
-under diagonal flow fields, including uniaxial and biaxial flow.
-Simulations under extensional flow may be carried out for an
-indefinite amount of time. It is an implementation of the boundary
-conditions from "(Dobson)"_#Dobson, and also uses numerical lattice
-reduction as was proposed by "(Hunt)"_#Hunt. The lattice reduction
-algorithm is from "(Semaev)"_Semaev. The fix is intended for
+This fix can be used to simulate non-equilibrium molecular dynamics
+(NEMD) under diagonal flow fields, including uniaxial and biaxial
+flow.  Simulations under continuous extensional flow may be carried
+out for an indefinite amount of time.  It is an implementation of the
+boundary conditions from "(Dobson)"_#Dobson, and also uses numerical
+lattice reduction as was proposed by "(Hunt)"_#Hunt. The lattice
+reduction algorithm is from "(Semaev)"_Semaev. The fix is intended for
 simulations of homogeneous flows, and integrates the SLLOD equations
 of motion, originally proposed by Hoover and Ladd (see "(Evans and
 Morriss)"_#Sllod).  Additional detail about this implementation can be
 found in "(Nicholson and Rutledge)"_#Nicholson.
 
+Note that NEMD simulations of a continuously strained system can be
+performed using the "fix deform"_fix_deform.html, "fix
+nvt/sllod"_fix_nvt_sllod.html, and "compute
+temp/deform"_compute_temp_deform.html commands.
+
 The applied flow field is set by the {eps} keyword. The values
 {edot_x} and {edot_y} correspond to the strain rates in the xx and yy
 directions.  It is implicitly assumed that the flow field is