Theoretical Study Of Electronic Structure And The Potential Energy Surface Of B And Be Compounds

This thesis consists of five chapters.In chapter 1, the theoretical background is presented, including the construction of the potential energy surface (PES) and the study of chemical dynamics. On the calculations of PES, the most popular and well-developed post HF methods at present are introduced. Some particular problems and the realization and characteristics of MRCISD are discussed as the main subjects.In the following two chapters, the electronic structures of BF(1∑+), BeF(2∑+), HBO(1A'), HBeO(2∑+), HBeF(1∑+), BBeB(1A1), H2BO(2B2), H3BO(1A'), BF-(2 ), BeF-(1∑+), HBO-(2A'), HBeO-(1∑+), HBeF-(2A'), BBeB-(2A1), H2BO-(1A1) and H3BO-(2A') are calculated at the B3LYP/6-311++G(3df,3pd) and G3 level. Besides, the potential energy curves of BeF (2∑+), BeF^1∑+, BF(1∑+), BF² , BF(3 ) and BF-(4∑- ) are constructed by CASSCF/MRCISD calculations. Stability of these molecules is discussed. The related results observed in measuring 10Be are well explained.Chapter 4 constructs the accurate potential energy profile for the 1A , 3A and3 A states of HBO by using the multi-reference two order perturbation theory (MRPT2) , and an interesting thing, a conical intersection, is found. Therefore, the intercoversion pathways from the linear HBO to the bend BOH are expounded based on the nature of the surfaces.The last chapter calculates the rate constant of the reaction of HBO-HOB. In appendix, the part codes of MRPT2 employed in the thesis are given.