Theoretical Study On Bonding Properties Of Alkali Metals And Rare Gases

Rare gas(Rg)elements with high chemical inertia include helium(He),neon(Ne),argon(Ar),krypton(Kr),xenon(Xe)and radon(Rn).Efforts to synthesize rare gas compounds had failed after it was discovered for a long time.Therefore,it is known as "Noble gas,Ng".Until 1962,Bartlett synthesized the first rare gas compound,Xe+[Pt F6]-,which shocked the academic community and marked the birth of a rare gas chemistry.Since then,more and more rare gas compounds have been synthesized by scientists.Nowdays,the bonding properties of metal and rare gas elements(as MNg F)become one of the main issues of theoretical and experimental research.In this work we calculate theoretically the rare gas alkali metal fluoridMNgF(M = Li,Na,K;Ng = Kr,Xe,Rn).We get some information about parameters of structure,infrared frequency and decomposition reaction energy and so on,and analyze the bonding properties between alkali metal and rare gases Kr,Xe and Rn.The main research contents are as following:Ab initio molecular orbital and density functional theory are used to optimize Li NgF,NaNg F and KNgF molecules for their ground state and transition state.We know the equilibrium structures,dissociation energies and decomposition reaction pathways and so on.The bonding nature of M-Ng and Ng-F in MNg F compounds(Ng = Kr,Xe and Rn,M = Li,Na and K)are examined by the atoms in molecules(AIM)approach and natural bond orbital(NBO)analysis.The results showed the the corresponding energy barriers protected Li Xe F(Li Rn F)from decomposition into Xe(Rn)+ Li F are calculated to be 7.5(13.8),4.8(10.0),and 5.2(10.7)kJ/mol for B3 LYP,MP2 and CCSD(T)levels of theory,respectively.While the stability of NaXe F and Na Rn F decreased comparing with Li Xe F and Li Rn F correspondingly.Theoretical research results showed that alkali metal compounds with xenon or radon are likely to be experimental observation.However,the alkali metal krypton compounds can be hardly synthesized due to their weak stability.According to the study of the bonding nature of Li Xe F,Li Rn F,Na XeF and NaRn F,the calculation results show that the Li-Xe,Na-Xe and Na-Rn are mainly weak bonding interaction with some ionic property,while the Li-Rn bond is weak bonding interaction with some covalent property.