聚合型硼氢化物(BH_3)_n(n=1—3)的几何结构与光谱的研究

Study on geometrical structure and spectrum of polymerization borohydride(BH_3)_n(n=1—3)

采用不同方法B3P86,B3LYP,MP2和LSDA,结合Dunning的相关一致基组cc-PVTZ,对聚合型硼氢化物(BH3)n(n=1—3)分子的可能几何构型进行优化计算,得出最稳定构型的几何参数、电子结构、振动频率和光谱等性质参数,并给出了最稳定结构的总能量(ET),结合能(EBT),平均结合能(Eav),电离势(EIP),能隙(Eg),费米能级(EF)等.结果表明:采用密度泛函DFT中的方法B3P86计算的能量最低,结构参数更接近文献值;三种硼氢化物分子基态都为1重态,电子态分别为1A',1A和1A;BH3分子的最稳定几何构型为平面三角形结构;B2H6为对称性乙烯式D2h立体结构,H—B之间生成氢桥式三中心双电子键;B3H9为C3ν立体结构,也生成氢桥式三中心双电子键,但三个氢桥三中心双电子键彼此隔离.最后分析了三种氢化物的红外和拉曼光谱、平均结合能、电离势、能隙和费米能级等特性,说明(BH3)n(n=1—3)三分子中B2H6最稳定,H—B桥键键长比端键更长,最强峰红外光谱强度最大.

The possible geometrical structures of polymerization borohydride（BH3）n（n=1—3） are optimized in computation,based on different methods of B3P86、B3LYP,MP2,LSDA and by combining the Dunning relevant and consistent base group cc-PVTZ.The configuration geometric parameter,the electronic structure,the vibrational frequency and spectrum of the most stable structure are obtained,and the total energy（ET）,binding energy（EBT）,the average binding energy（Eav）,the ionization potential（EIP）,the energy crack（Eg）,the Fermi level（EF） and so on are also given.The results indicate that the total energy is lowest and its value is close to the reported values from B3P86 method.The ground state of the three kinds of borohydride are all singlet states,the ir electronic states respectively are 1A＇,1A,and 1A.The stable geometry configuration of BH3 molecule is the planar triangle,B2H6 has a symmetrical ethylene type D2hspatial structure,and between H-B produces the hydrogen bridge type with three-center double electronic key,B3H9 has a C3νspatial structure,also produces a hydrogen bridge type of three-center double electronic key,but the three hydrogen bridge types are isolated from each other.Finally the infrared and the Raman spectrum,the average binding energy,the ionization potential,the energy gap,Fermi level and so on are analyzed.B2H6 is shown to be the most stable molecule in（BH3）n（n=1—3）,the H-B bridge bond key long is longer than the terminal lond,the infrared intensity of strongest peak is a maximal value.