diff --git a/doc/fix_atom_swap.html b/doc/fix_atom_swap.html
index fc3cd17bc4..b6f9192562 100644
--- a/doc/fix_atom_swap.html
+++ b/doc/fix_atom_swap.html
@@ -29,10 +29,10 @@
 
 <LI>one or more keyword/value pairs may be appended to args 
 
-<LI>keyword = <I>types</I> or <I>delta_mu</I> or <I>ke</I> or <I>semi-grand</I> or <I>region</I> 
+<LI>keyword = <I>types</I> or <I>mu</I> or <I>ke</I> or <I>semi-grand</I> or <I>region</I> 
 
 <PRE>  <I>types</I> values = two or more atom types
-  <I>delta_mu</I> values = chemical potential of swap types (energy units)
+  <I>mu</I> values = chemical potential of swap types (energy units)
   <I>ke</I> value = <I>no</I> or <I>yes</I>
     <I>no</I> = no conservation of kinetic energy after atom swaps
     <I>yes</I> = kinetic energy is conserved after atom swaps
@@ -48,7 +48,7 @@
 </P>
 <PRE>fix 2 all atom/swap 1 1 29494 300.0 ke no types 1 2
 fix myFix all atom/swap 100 1 12345 298.0 region my_swap_region types 5 6 
-fix SGMC all atom/swap 1 100 345 1.0 semi-grand yes types 1 2 3 delta_mu 4.3 -5.0 
+fix SGMC all atom/swap 1 100 345 1.0 semi-grand yes types 1 2 3 mu 4.3 -5.0 
 </PRE>
 <P><B>Description:</B>
 </P>
@@ -94,13 +94,14 @@ conversion. An attempt is made to switch
 the selected atom (if eligible) to one of the other listed types 
 with equal probability. Acceptance of each attempt depends upon the Metropolis criterion.
 </P>
-<P>The <I>delta_mu</I> keyword allows users to specify non-zero chemical
-potentials for each of the atom types. All chemical potentials are
-absolute, so there should be one for each swap type listed following
-the <I>types</I> keyword. 
-These parameters are required for semi-grand canonical
-ensemble simulations where it may be desirable to actively control the
-composition of the system.  
+<P>The <I>mu</I> keyword allows users to specify chemical
+potentials. This is required and allowed only when using <I>semi-grand</I>. 
+All chemical potentials are absolute, so there is one for 
+each swap type listed following the <I>types</I> keyword. 
+In semi-grand canonical ensemble simulations the chemical composition 
+of the system is controlled by the difference in these values. So
+shifting all values by a constant amount will have no effect
+on the simulation.
 </P>
 <P>This command may optionally use the <I>region</I> keyword to define swap
 volume.  The specified region must have been previously defined with a
@@ -187,7 +188,7 @@ LAMMPS</A> section for more info.
 </P>
 <P><B>Default:</B>
 </P>
-<P>The option defaults are ke = yes, semi-grand = no, delta_mu = 0.0 for 
+<P>The option defaults are ke = yes, semi-grand = no, mu = 0.0 for 
 all atom types.
 </P>
 <HR>
diff --git a/doc/fix_atom_swap.txt b/doc/fix_atom_swap.txt
index 726c685aa1..245af6d88f 100644
--- a/doc/fix_atom_swap.txt
+++ b/doc/fix_atom_swap.txt
@@ -19,9 +19,9 @@ X = number of swaps to attempt every N steps :l
 seed = random # seed (positive integer) :l
 T = scaling temperature of the MC swaps (temperature units) :l
 one or more keyword/value pairs may be appended to args :l
-keyword = {types} or {delta_mu} or {ke} or {semi-grand} or {region} :l
+keyword = {types} or {mu} or {ke} or {semi-grand} or {region} :l
   {types} values = two or more atom types
-  {delta_mu} values = chemical potential of swap types (energy units)
+  {mu} values = chemical potential of swap types (energy units)
   {ke} value = {no} or {yes}
     {no} = no conservation of kinetic energy after atom swaps
     {yes} = kinetic energy is conserved after atom swaps
@@ -36,7 +36,7 @@ keyword = {types} or {delta_mu} or {ke} or {semi-grand} or {region} :l
 
 fix 2 all atom/swap 1 1 29494 300.0 ke no types 1 2
 fix myFix all atom/swap 100 1 12345 298.0 region my_swap_region types 5 6 
-fix SGMC all atom/swap 1 100 345 1.0 semi-grand yes types 1 2 3 delta_mu 4.3 -5.0 :pre
+fix SGMC all atom/swap 1 100 345 1.0 semi-grand yes types 1 2 3 mu 4.3 -5.0 :pre
 
 [Description:]
 
@@ -82,13 +82,14 @@ conversion. An attempt is made to switch
 the selected atom (if eligible) to one of the other listed types 
 with equal probability. Acceptance of each attempt depends upon the Metropolis criterion.
 
-The {delta_mu} keyword allows users to specify non-zero chemical
-potentials for each of the atom types. All chemical potentials are
-absolute, so there should be one for each swap type listed following
-the {types} keyword. 
-These parameters are required for semi-grand canonical
-ensemble simulations where it may be desirable to actively control the
-composition of the system.  
+The {mu} keyword allows users to specify chemical
+potentials. This is required and allowed only when using {semi-grand}. 
+All chemical potentials are absolute, so there is one for 
+each swap type listed following the {types} keyword. 
+In semi-grand canonical ensemble simulations the chemical composition 
+of the system is controlled by the difference in these values. So
+shifting all values by a constant amount will have no effect
+on the simulation.
 
 This command may optionally use the {region} keyword to define swap
 volume.  The specified region must have been previously defined with a
@@ -175,7 +176,7 @@ LAMMPS"_Section_start.html#start_3 section for more info.
 
 [Default:]
 
-The option defaults are ke = yes, semi-grand = no, delta_mu = 0.0 for 
+The option defaults are ke = yes, semi-grand = no, mu = 0.0 for 
 all atom types.
 
 :line