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NH_2＋H→NH＋H_2反应的IRC和速率常数的理论研究.docx

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NH_2＋H→NH＋H_2反应的IRC和速率常数的理论研究 Introduction: TheNH2+Hreactionhasbeenasubjectofinterestforquantumchemistrycalculationsbecauseofitsimportanceinhydrogencombustionchemistry.Thisreactionplaysacrucialroleintheproductionofnitricoxideandhydrogenatomsincombustionreactions,whichareimportantfortheunderstandingofatmosphericandcombustionchemistry.Inthispaper,wewilldiscussthetheoreticalstudyofthereactionmechanism,potentialenergysurface,andrateconstantsoftheNH2+H→NH+H2reaction. PotentialEnergySurface: Thepotentialenergysurface(PES)oftheNH2+Hreactionhasbeencalculatedusingabinitioquantumchemistrymethods.Thereactionpathwayisusuallydividedintotwostages:Theinitialreactionstage,wherethediatomichydrogencollideswithNH2,leadingtotheformationofatransitionstate,andthesecondstage,wherethetransitionstateleadstotheformationofNHandH2.Thepotentialenergysurfaceisacrucialtoolforunderstandingthereactionmechanism,anditprovidesafundamentaltheoreticalbasisfordeterminingthereactionrateconstants. ReactionMechanism: ThereactionmechanismfortheNH2+H→NH+H2reactioncanbedescribedasfollows.TheinitialcollisionofhydrogenwiththeNH2moleculeresultsintheformationofacollisioncomplex,whichthenundergoesisomerizationintoatransitionstate.Thetransitionstateisanintermediatestatebetweenthereactantsandproducts,andithashighpotentialenergy.ThetransitionstateeventuallyleadstotheformationofNHandH2throughtwopossiblechannels:thedirectchannelandtheroamingchannel.Thedirectchannelinvolvesatraditionaltransitionstate,whereastheroamingchannelinvolvesalong-rangeinteractionbetweentheNH2andHatoms. RateConstants: TherateconstantsfortheNH2+H→NH+H2reactionhavebeencalculatedusingdifferenttheoreticalmethods,includingvariationaltransitionstatetheory(VTST)andcanonicalvariationaltheory(CVT).TheVTSTmethodhasbeenwidelyusedforcalculatingtherateconstantsofchemicalreactions,whereastheCVTmethodhasbeenusedtoaccountforthenon-classicalbehaviorthatmayoccurduringthereaction.Therateconstantshavealsobeeninvestigatedoverarangeoftemperaturesandpressures,leadingtoa