External parameters for Mopac calculations



Dear all,
 I want to perform computations on Mg containing systems using Mopac6.0 and
 found an article in which a magnesium parameter set has been published for
 use with AM1 (i.e. J. Chem. Phys. B, vol. 102(41), 1998, 8083).  I want to
 plug in these parameters into Mopac6.0 by using the keyword
 EXTERNAL=filename with filename the name of a file containing the new
 parameter set in the format <parameter> Mg <Value of parameter> and
 terminated by a blank line.  However, I appear to do something wrong as I
 keep getting the message 'SOME ELEMENTS HAVE BEEN SPECIFIED FOR WHICH NO
 PARAMETERS ARE AVAILABLE.  CALCULATION STOPPED'.  Has anybody an idea about
 what could possibly be wrong?
 Thanks in advance for the help!
 Betty
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