Abstract: The electronic structures of Dawson HPA anion(P₂M₁₈O₆₂)^6-(M=Mo,W) have been calculat-ed by the discrete variational method coupled with the first principle density functional theory (DFT-DVM).The results show that the difference of the chemical properties of polar and equator sites exists.The reduction electrons will be introduced mainly into equatorial metal atoms.The active centers of(P₂Mo₁₈O₆₂)^6- are Mo, Opb, Oet, Oei and that of (P₂W₁₈O₆₂)^6- are W, Opb, Oet The redox effect of(P₂Mo₁₈O₆₂)^6- is stronger than that of (P₂W₁₈O₆₂)^6-, but their acidities are quite the opposite, which areall the same as those of (PM₁₂O₄₀)_3- (M=Mo, W).

Key words: Dawson HPA anion, (P₂Mo₁₈O₆₂)^6-, (P₂W₁₈O₆₂)^6-, Elecrtronic structure, Density function theory(DFT), Discrete variational method(DVM)