平面B_nBe(n=1～7)团簇的结构和稳定性理论研究

A Theoretical Study on Structure and Stability of Planar B_nBe(n=1～7)

运用密度泛函理论(DFT)对平面B n Be(n=1～7)的结构、稳定性及势能面进行了计算.通过计算得到了B n Be(n=1～7)团簇的最稳定结构.值得注意的是,B n Be(n=1～7)团簇的结构模式转变发生在n=1到n=2之间.平均原子成键能(BE)、成键能增量(IBE)、能量二次差分(Δ2E)和能隙(ΔE)的变化图揭示了B4Be和B7Be具有较高的稳定性.结果表明,B n Be(n=1～7)团簇的稳定性与离域π分子轨道、σ正切分子轨道和σ径向分子轨道的相互作用有关.价分子轨道和核独立化学位移(NICS)的分析证明异构体B n Be(n=2～5)都具有π-芳香性.理论分析表明,B4Be具有σ-和π-双芳香性.有趣的是,在CCSD(T)/6-311+G(d)//B3LYP/6-311+G(d)水平上,B4Be是热力学上和动力学上稳定的,可能在将来的实验中观察到.

The structures, stabilities, bonding nature, and potential energy surfaces of Bn Be （ n = 1 ～ 7 ） are systematically explored and investigated based on density functional theory（DFF）. The lowest-energy structures for BnBe（ n= 1 ～7 ）are located. It is worthy to note that a structural transition occurs from n = 1 to n = 2 for B, Be （ n = 1 ～7 ）. The evolution of the binding energy per atom, incremental binding energy, second order difference of total energy, and energy gap with the size of B, Be reveals that the lowest-energy isomers B4 Be and B7 Be are highly stable. The results demonstrate that the stability of lowest-energy isomers of B~ Be （ n = 1 ～ 7 ） is attributed to the delocalized or, Q-radial, and Q-tangential molecular orbitals （MOs）interactions. BnBe（ n = 2 ～ 5 ）exhibit π aromaticity from valence molecular orbital analysis and nucleus in- dependent chemical shifts （NICSs）values. B4 Be exhibit Q- and or-double aromaticity in terms of theoretical analyses. In- terestingly, B4Be is stable both thermodynamically and kinetically,which may be observable in future experiment.