Hi Bahman,
a more recent version of Lammps would give a more descriptive error message, but:
In pair_coeff commands I inserted below parameters required for simulation of Mg according to this paper(Modelling Simul. Mater. Sci. Eng. 23 (2015) 015004 (19pp)):
re = 3.19
Cmin = 0.49
Cmax = 2.90
Please compare the precise syntax to that given in the documentation. In particular, you're missing the element indices of what these quantities apply to.
Best,
Sebastian