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

The molecular potential energy function is one of important research for 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. Not only does the function reflect the microstructure andspectroscopic properties of molecular, but also it is the basis for the study ofmolecular reaction dynamics. The function plays an important role on clusterformation, stability and dissociation. A large number of spectral data and structuralparameters in the fields, such as aerospace, laser and materials technology arenecessary for potential energy function. Therefore, the functions of diatomic andtriatomic molecule have been reported by researchers.For the past decades, borides materials and alloy of Al and Li are widelyconcerned and theoretic and experimental study about it has achieved a greatprogress. However, by now, the investigation of potential energy functions forborides materials and alloy of Al and Li are still very limited. Therefore, in this paper,the parameters of B₂, M₂, MB, MB₂and M₂B （M=Al, Li） have achieved bycoupled-cluster theory. Potential energy functions of them have been achieved byfitting and nonlinear optimization.First of all, coupled cluster （CCSD） method has been used to optimize theground state structures of B₂、M₂and MB（M=Al, Li） molecular with a variety ofbasis set. Compared with existing experimental and theoretical values and selectthe optimal basis set for B₂、M₂and MB（M=Al, Li） molecule. The potentialenergy surfaces of them have been scanned and derived by the least-squarefitting method. According to the relationship of the force constants and potentialenergy parameters, and relationship between the force constants and spectroscopicconstants, and export the corresponding spectroscopic constants. The result show thatscanned data is in good agreement with fitting data, and spectroscopic constants arein good agreement with experimental values.Moreover, for the triatomic molecular, the same method with diatomicmolecular has been used to optimize the ground state, and the stable structureparameter, dissociation energy, resonant frequency and force constant have beenreceived. Their dissociation limits of MB₂，M₂B（M=Al, Li） are induced byemploying the group theory, energy optimal principle and the reversible principles ofmicroscopic processes. On this basis, the potential energy functions of MB₂and M₂B have been derived from the many-body expansion theory, and the threeequivalent potential energy diagrams have been drawn according to thepotential energy function. The diagrams are the scale that the energy surfacewhether conform the triatomic molecular geometry from different angles.Results show that the analytical potential energy function accuratelyreproduces the structural features of molecular.