简介：Inthispaper,theenergy,equilibriumgeometry,andharmonicfrequencyofthegroundelectronicstateofPO2arecomputedusingtheB3LYP,B3P86,CCSD(T),andQCISD(T)methodsinconjunctionwiththe6-311++G(3df,3pd)andcc-pVTZbasissets.AcomparisonbetweenthecomputationalresultsandtheexperimentalvaluesindicatesthattheB3P86/6-311++G(3df,3pd)methodcangivebetterenergycalculationresultsforthePO2molecule.ItisshownthatthegroundstateofthePO2moleculehasC2vsymmetryanditsgroundelectronicstateisX2A1.TheequilibriumparametersofthestructureareRPO=0.1465nm,∠OPO=134.96°,andthedissociationenergyisEd=19.218eV.Thebentvibrationalfrequencyν1=386cm-1,symmetricstretchingfrequencyν2=1095cm-1,andasymmetricstretchingfrequencyν3=1333cm-1areobtained.Onthebasisofatomicandmolecularreactionstatics,areasonabledissociationlimitforthegroundstateofthePO2moleculeisdetermined.ThentheanalyticpotentialenergyfunctionofthePO2moleculeisderivedusingmany-bodyexpansiontheory.ThepotentialcurvescorrectlyreproducetheconfigurationsandthedissociationenergyforthePO2molecule.

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