Electronic, energetic, and structural properties of C- and Si-doped Mg12O12 nano-cages

We have performed density functional theory calculations to investigate the influence of doping of C and Si atoms on the geometric, electronic, solvation, energetic, and field emission properties of a MgO nano-cage. It has been found that substitution of one of the Mg atoms of the nano-cage by either C or Si atom is energetically favorable while substituting an O atom with both of them is unfavorable. It has been also found that replacing Mg or O atom of the cluster by one C atom much more increases its conductance than that by Si one. In fact, HOMO/LUMO gap (Eg) of the cluster is reduced from 4.86 to 1.11 eV, upon replacing Mg atom by C. Based on the obtained results, substituting a Mg atom by either C or Si atom may significantly increase the field electron emission current from the cluster surface by reducing its work function. Overall, doping of Mg12O12 nano-cage by either C or Si atom increases its solubility, conductance, electric dipole moment, kinetic stability, and field electron emission while decreases the Eg and work function.