enable LAMMPS/VASP coupling to work w/out using VASP

examples/COUPLE/lammps_vasp/README

@@ -36,9 +36,11 @@ You can leave off the -z if you do not have ZMQ on your system.
 
 Prepare to use VASP and the vasp_wrapper.py script
 
-You can run the vasp_wrap.py script as-is to test that the
-coupling between it and LAMMPS is functional.  But the as-is
-version will not attempt to run VASP.
+You can run the vasp_wrap.py script as-is to test that the coupling
+between it and LAMMPS is functional.  This will use the included
+vasprun.xml file output by a previous VASP run.
+
+But the as-is version of vasp_wrap.py will not attempt to run VASP.
 
 To do this, you must edit the 1st vaspcmd line at the top of
 vasp_wrapper.py to be the launch command needed to run VASP on your
@@ -63,6 +65,8 @@ Note that the POSCAR_template file should be matched to the LAMMPS
 input script (# of atoms and atom types, box size, etc).  The provided
 POSCAR_W matches in.client.W.
 
+Once you run VASP yourself, the vasprun.xml file will be overwritten.
+
 NOTE: explain how vasp_wrapper.py finds the cslib.py wrapper on the
 CSlib to import.