Barrier Heights in Quantum Monte Carlo with Linear-Scaling Generalized-Valence-Bond Wave Functions

We
investigate here the performance of our recently developed linear-scaling
Jastrow-generalized-valence-bond (J-LGVB) wave functions based on
localized orbitals, for the quantum Monte Carlo (QMC) calculation
of the barrier heights and reaction energies of five prototypical
chemical reactions. Using the geometrical parameters from the Minnesota
database collection, we consider three hydrogen-exchanges, one heavy-atom
exchange, and one association reaction and compare our results with
the best available experimental and theoretical data. For the three
hydrogen-exchange reactions, we find that the J-LGVB wave functions
yield excellent QMC results, with average deviations from the reference
values below 0.5 kcal/mol. For the heavy-atom exchange and association
reactions, additional resonance structures are important, and we therefore
extend our original formulation to include multiple coupling schemes
characterized by different sets of localized orbitals. We denote these
wave functions as J-MC-LGVB, where MC indicates the multiconfiguration
generalization, and show that such a form leads to very accurate barrier
heights and reaction energies also for the last two reactions. We
can therefore conclude that the J-LGVB theory for constructing QMC
wave functions, with its multiconfiguration generalization, is valid
for the study of large portions of ground-state potential energy surfaces
including, in particular, the region of transition states.

本研究深入探讨了我们近期开发的基于局域轨道的线性缩放Jastrow广义价键（J-LGVB）波函数在量子蒙特卡洛（QMC）计算五种典型化学反应的势垒高度和反应能量方面的性能。我们采用明尼苏达数据库收集的几何参数，考虑了三种氢交换反应、一种重原子交换反应以及一种结合反应，并将我们的结果与现有的最佳实验和理论数据进行了比较。对于三种氢交换反应，我们发现J-LGVB波函数在QMC计算中取得了优异的结果，其平均偏差低于0.5 kcal/mol。对于重原子交换和结合反应，多重共振结构的重要性不可忽视，因此我们对原始公式进行了扩展，纳入了由不同局域轨道集表征的多种耦合方案。我们将这些波函数命名为J-MC-LGVB，其中MC代表多配置泛化，并证实这种形式对于最后两个反应同样能导致非常精确的势垒高度和反应能量。因此，我们可以得出结论，J-LGVB理论在构建QMC波函数方面，凭借其多配置泛化，适用于研究大量基态势能面，特别是过渡态区域的化学过程。