AB-INITIO EFFECTIVE CORE POTENTIAL CALCULATIONS ON HGI2, PTI2, AND PBI2

Ab initio methods have applied to HgI2, PtI2, and PbI2 to assess the p erformance of relativistic effective core potentials (RECPs) on ground -state properties of heavy-metal iodides. With electron correlation in cluded via Moller-Plesset (MP) theory up to third order, good agreemen t with experiment was found for the mercury and lead compounds. PtI2 i s also bent in its ground state, with a bond angle near to 96 degrees. In terms of bond strength, the following order was found (most stable first): Pb-I > Pt-I > Hg-I. Harmonic vibrational frequencies and ioni zation potentials are also reported. The direction of the first nonzer o moment indicates that the metal atom is effectively positively charg ed in all three molecules. In HgI2, fourth-order MP corrections are sh own to be unimportant.