Updated doc (use of overlap clarified)

doc/src/create_atoms.rst

@@ -314,6 +314,16 @@ radius is taken into account so that all new molecules will be created
 at locations not closer than (*radius* + molecule radius) from the location
 of any existing atom in the system.
 
+.. note::
+
+   Checking for overlaps is a very costly operation (O(N) for each new atom/molecule,
+   where N is the number of existing atoms) and the intended use of this keyword is,
+   for example, adding small amounts of new atoms/molecules to relatively sparse systems
+   mid simulation (between consecutive runs), i.e. where running an energy minimization
+   procedure isn't an option.  
+   In any case, the use of the *maxtries* keyword in combination with *overlap* is
+   highly recommended.
+
 The *units* keyword determines the meaning of the distance units used
 to specify the coordinates of the one particle created by the *single*
 style.  A *box* value selects standard distance units as defined by

src/create_atoms.cpp

@@ -769,10 +769,7 @@ void CreateAtoms::add_random()
 
       if (overlapflag) {
         int reject_local = 0;
-        //TODO this could be done only on the proc where coords are
-        // (using local + ghost atoms), BUT it is possible that
-        // ocutsq > skin^2 (although highly unlikely... warning?)
-        // This is only relevant for highly inhomogeous systems... ?
+        // Could be done more efficiently... (only on proc where coords are?)
         for (int i = 0; i < nlocal; i++) {
           delx = xone[0] - x[i][0];
           dely = xone[1] - x[i][1];