Study On The Potential Energy Function And Spectroscopic Constants Or Six(X=0,F,S) Molecule

The molecular potential energy function is the theoretical foundations of studying atomicand molecular physics It is reflected in the following aspects.The potential energy function is thewhole description of the molecular energy structure and spectroscopyconstants.The potentialenergy function of diatomic molecular is the foundation of structuring for polyatomic molecule.Because macromolecules can be regarded as multiple diatomic molecular.The potential energyfunction is provided information for investigating atomic and molecular collision and molecularreaction dynamics,and the basis of molecular stability. In the last few decades, researchers haveproposed the method and deduced the potential energy function and the structure of moleculefrom theoretical computation.In this paper,we investigat SiX（X=O,F,S）molecule of the ground state structure,potentialfunction and spectroscopy constants using density functional theory(DFT).The main contents arepresented as the following:In chapter1and2,we give significance and a brief introduction to potential energyfunction.At first,we introduced the research and meaning of diatomic molecules potentialenergy function.Then, we introduced the molecular structure and molecular potential energyfunction of the basie theory,including Born-Oppenheimer approximation and two basietheory---atomic molecular reaction statics principle and molecular dissociation limits.Some basicgeneral properties and relationship with spectroscopy constants of potential energy function havebeen briefly summered.Density Functional Theory and ab initio are introduced in the first half of chapter3. weintroduce exchang functional and correlation functional,and instruct some calculation methodstogether with exchange functional and the correlation functional when using density functionaltheory.In the last half of chapter3,the electronic states of the ground state dissociation limit ofSiX（X=O,F,S） molecule are correctly determined based on atomic and molecular reactionstaties principle.The structural optimization for the ground state of SiX（X=O,F,S）molecule havebeen calculated using density functional theory B3LYP and B3P86method from Gaussion03software with the basis sets6-311++G(3df,2pd) and D95(3df,2pd).Based on obtaining the stablestructures，the potential curve of the ground state is scanned by using B3P86/D95(3df,2pd).Scan points are made into two-dimensional curve by using Origin software and Murrell-Sorbiefunction fitted to potential energy curve. In order to verify the Murrel-Sorbie function accuracy，accoiding to relationship between the parmeters and force constant,we can calculate the forceconstant.Further we can determine some spectroscopy constants,such as harmonic vibrational frequencyω e,the inharmonic vibratioal factorω e χ e,the rigid-rotational factorBe,thenonrigid-rotational factorα e.We compared the results with the present experimental values andother theoretical results.These comparison show that all calculation results,such as thedissociation energy,the equilibrium internuclear distance and spectroscopy constants,are betteragreement with experimental results. All these phenomena indicate that Murrell-Sorbie functioncan accurately describe the ground state of SiX（X=O,F,S）molecule.