用扩散蒙特卡罗方法研究BH2、B（0H）2、BCl2和BCI的键离解能

Diffusion Monte Carlo Study of Bond Dissociation Energies for BH2, B（OH）2, BCl2, and BCI

采用扩散蒙特卡罗（DMC）方法计算了BH2、B（OH）2、BCl2和BCl的HB—H和HOB—OH的键离解能，同时也研究了轨道选择和Backflaw变换对DMC计算结果的影响．在Slater-Jastrow DMC（SJ—DMC）计算方法中，当采用B3PW91轨道时得到的HB—H和HOB-OH键离解能分别是359．1±0．12和98．2±0．12kJ／mol；用B3LYPSJ—DMC计算键离解能得到r与用B3PW91SJ—DMC方法类似的结果．通过BF—DMCf即在DMC中引入backflow修正）计算得到的HB—H键离解能为369．6±0．12kJ／mol，也得到了更加接近实验值的HOB-OH键离觯能为446．0±1．84kJ／mol．由DMC的计算结果可以断定HB—H的键离解能的实验值为375．8kJ／mol．另外还给出了BCl2和BCl的键离解能的计算结果．

On basis of bond dissociation energies （BDEs） for BH2, B（OH）2, BCl2, and BCl, the diffusion Monte Carlo （DMC） method is applied to explore the BDEs of HB-H, HOB-OH, ClB-Cl, and B-Cl. The effect of the choice of orbitals, as well as the backflow transformation, is studied. The Slater-Jastrow DMC algorithm gives BDEs of 359.1±0.12 kJ/mol for HB-H, 410.5±0.50 kJ/mol for HOB-OH, 357.8±1.46 kJ/mol for ClB-Cl, and 504.5±0.96 kJ/mol for B-Cl using B3PW91 orbitals and similar BDEs when B3LYP orbitals are used. DMC with backflow corrections （BF-DMC） gives a HB-H BDE of 369.9±0.12 kJ/mol which is close to one of the available experimental value （375.8 kJ/mol）. In the case of HOB-OH BDE, the BF-DMC calculation is 446.04-1.84 k J/mol that is closer to the experimental BDE. The BF-DMC BDE for ClB-Cl is 343.2±2.34 kJ/mol and the BF-DMC B-Cl BDE is 523.3±0.33 kJ/mol, which are close to the experimental BDEs, 341.9 and 530.0 kJ/mol, respectively.