diff --git a/doc/src/mdi.rst b/doc/src/mdi.rst
index 2f7fc65852..cdb5e432cc 100644
--- a/doc/src/mdi.rst
+++ b/doc/src/mdi.rst
@@ -17,7 +17,7 @@ Syntax
      *engine* args = zero or more keyword/args pairs
        keywords = *elements*
          *elements* args = N_1 N_2 ... N_ntypes
-           N_1,N_2,...N_ntypes = atomic number for each of ntypes LAMMPS atom types
+           N_1,N_2,...N_ntypes = chemical symbol for each of ntypes LAMMPS atom types
      *plugin* args = name keyword value keyword value ...
        name = name of plugin library (e.g., *lammps* means a liblammps.so library will be loaded)
        keyword/value pairs in any order, some are required, some are optional
@@ -35,7 +35,7 @@ Examples
 .. code-block:: LAMMPS
 
    mdi engine
-   mdi engine elements 13 29
+   mdi engine elements Al Cu
    mdi plugin lammps mdi "-role ENGINE -name lammps -method LINK" &
               infile in.aimd.engine extra "-log log.aimd.engine.plugin" &
               command "run 5"
@@ -173,13 +173,16 @@ commands, which are described further below.
    atom type values are consistent in both codes, then the >TYPES
    command can be used.  If not, the optional *elements* keyword can
    be used to specify what element each LAMMPS atom type corresponds
-   to.  This is specified by the atomic number of the element (e.g., 13
-   for Al).  An atomic number must be specified for each of the ntypes
-   LAMMPS atom types.  Ntypes is typically specified via the
-   create_box command or in the data file read by the read_data
-   command.  In this has been done, the MDI driver can send an
-   >ELEMENTS command to the LAMMPS driver with the atomic number of
-   each atom.
+   to.  This is specified by the chemical symbol of the element,
+   e.g. C or Al or Si.  A symbol must be specified for each of the
+   ntypes LAMMPS atom types.  Each LAMMPS type must map to a unique
+   element; two or more types cannot map to the same element.  Ntypes
+   is typically specified via the :doc:`create_box <create_box>`
+   command or in the data file read by the :doc:`read_data
+   <read_data>` command.  Once this has been done, the MDI driver can
+   send an >ELEMENTS command to the LAMMPS driver with the atomic
+   number of each atom and the LAMMPS engine will be able to map it to
+   a LAMMPS atom type.
 
 The MD and OPTG commands perform an entire MD simulation or energy
 minimization (to convergence) with no communication from the driver