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用ab initio MP2/3 21G~*方法,对四角锥型硼化物B_4H_8X(X=Li~-,Be,B~+,C~(2+),B,C,N~+,BeH,BH和CH~+)及其碎片B_4H_8的结构进行了研究.结果表明,在B_4H_8X结构中,端氢(H_t)的位置受顶点帽基X的支配.帽基原子的电负性较小和配位原子轨道的弥散程度较大时,H_t处在B_n环平面下方,与帽基反向.反之,H_t与帽基同向.桥氢(H_b)的位置总是在B_n环平面之下,与X反向.进一步研究了B_4H_8X的离解能,并进行了电子相关能校正.发现结构1和2稳定性较差,结构3～10较稳定.分子碎片B_4H_8的最稳定构型为2112结构.
The tetrapod boride B_4H_8X (X = Li ~ -, Be, B ~ +, C ~ (2 +), B, C, N ~ +, BeH, BH and CH ~ +) and its fragment B_4H_8 were studied.The results showed that the position of terminal hydrogen (H_t) in the B_4H_8X structure is dominated by the peak cap X. The electronegativity of the capped atoms is smaller and the coordination atoms When the orbital dispersion is large, H_t is located below the B_n ring plane and opposite to the cap base, whereas H_t is the same direction as the cap base. The position of bridging hydrogen (H_b) is always below the B_n ring plane, The dissociation energies of B_4H_8X were further studied, and the correlation energies of B_4H_8X were also calibrated.It was found that the structures 1 and 2 were less stable and the structures 3 ~ 10 were more stable.The most stable configuration of molecular fragment B_4H_8 was 2112 structure.