SUMMARY
The Mott - Hubbard metal - insulator transition in the half-filled mass imbalanced ionic Hubbard model is investigated using the two-site dynamical mean field theory. We find that for a fixed mass imbalanced parameter r the critical interaction Uc increases when the ionic energy ?\Delta is increased. In the other hand, for a fixed ?\Delta, UcU_c decreases with increasing the mass imbalance. We also show the existence of BI phase in the system for the case ??0\Delta \ne 0, U=0U=0 and calculate the staggered charge density nB-nAn_B - n_A as a function of the interaction for different values of the mass imbalance. Our results in the limiting cases (r=1r = 1; ??0\Delta \ne 0 or/and ?=0\Delta = 0; r?1r\ne 1) are in good agreement with those obtained from full dynamical mean field theory.