The Potential Function Of Ground State For Borides Molecules MB₂、M₂B（M=Na,B）

The molecular potential energy function is one of the important fields in atomicand molecular physics. On the basis of B-O approximate, it is a complete descriptionof molecular properties. That is the description of energy, geometry, mechanics andspectroscopic properties.The function plays an important role on cluster formation,stability and dissociation. A large number of spectral data and structural parametersin the fields, such as aerospace, laser and materials technology are necessary forpotential energy function. Therefore, the functions of diatomic and triatomicmolecule have been reported by researchers.For the past decades, borides materials and alloy of Na and Small boron clustersare widely concerned and theoretic and experimental study about it has achieved agreat progress. However, by now, the investigation of potential energy functions forborides materials and alloy of Na and Small boron clusters are still very limited.Therefore, in this paper, the parameters of B₂, M₂, MB, MB₂and M₂B （M=Na, B）have achieved by coupled-cluster theory. Potential energy functions of them havebeen achieved by fitting and nonlinear optimization.First of all, coupled cluster （CCSD） method has been used to optimize theground state structures of B₂、Na₂andNaB molecular with a variety of basis set.Compared with existing experimental and theoretical values and select theoptimal basis set for B₂、Na₂andNaB molecule. The potential energy surfacesof them have been scanned and derived by the least-square fitting method.According to the relationship of the force constants and potential energy parameters,and relationship between the force constants and spectroscopic constants, and exportthe corresponding spectroscopic constants. The result show that scanned data is ingood agreement with fitting data, and spectroscopic constants are in good agreementwith experimental values.The ground state structures of MB₂and M₂B （M=Na, B）have been optimized by thesame method and basis set. By using the B₂、Na₂and NaB molecular’s balance structure geometric parameters, the force constant, dissociation energy and the function relations of thelinear and nonlinear coefficients, and in terms of a nonlinear optimization fitting made in the nearminimum point of MB₂and M₂B （M=Na, B） molecular potential energy surface, thenonlinear coefficients and then the linear coefficients Ci（i=1,2,3,4,5,6,7） are obtained. Withthe many-body expansion, the completely analytical potential energy functions of ground state ofthe MB₂and M₂B （M=Na, B） molecular are also derived. The ground state equilibriumgeometries of MB₂and M₂B （M=Na, B） are reproduced by the completely potential energyfunctions and shown in the potential energy surfaces exactly.