semi-empirical parameters for Mg

 Dear Netters,
 My friend would like to know something about semi-empirical
 parameters of Mg.
 The PM3 understimates the bond lenght Mg-X (for example in Mg-Cl2
 the PM3 computed distance Mg-Cl is 1.887, while the experimental one
 is 2.186.  In some complexes the Mg-O PM3 distance is about 1.87 but
 the experimental ones are about 2.10.
 Are there AM1 parameters for Mg atom or refined from original
 reference of PM3 ( J. Comp. Chem. 1991) which works better for
 these kind of systems ?
 Thanks in advance
 Pino Milano
 Pino Milano
 University of Salerno
 e-mail pino