标题： 非共价相互作用的固定节点扩散蒙特卡罗计算中的基组不完备误差 显示英文标题

标题： Basis set incompleteness errors in fixed-node diffusion Monte Carlo calculations on non-covalent interactions

摘要： 基组不完备误差（BSIE）是量子化学（QC）计算中常见的误差来源，但在固定节点扩散蒙特卡洛（FN-DMC）计算中尚未得到全面研究。由于FN-DMC是一种投影方法，通常认为它受基组偏差的影响最小。 然而，我们发现这一假设并不总是成立。虽然小基组引起的总FN-DMC能量的相对误差较小，但在弱相互作用系统的结合能（$E_{\rm b}$）评估中可能变得显著。我们系统地研究了基于FN-DMC的结合能（$E_{\rm b}$）评估中的BSIEs，使用了A24数据集，这是一个著名的包含24个非共价键二聚体的基准数据集。 与普遍预期相反，我们发现当采用如cc-pVDZ等小局域化基组时，FN-DMC评估中的$E_{\rm b}$确实存在显著的BSIEs。我们观察到，在氢键相互作用的二聚体中BSIEs较大，在色散主导的相互作用中则较小。我们还发现，通过添加弥散轨道、使用对消（CP）校正或两者结合，可以有效减轻BSIEs。 显示英文摘要

摘要： Basis set incompleteness error (BSIE) is a common source of error in quantum chemistry (QC) calculations, but it has not been comprehensively studied in fixed-node Diffusion Monte Carlo (FN-DMC) calculations. FN-DMC, being a projection method, is often considered minimally affected by basis set biases. Here, we show that this assumption is not always valid. While the relative error introduced by a small basis set in the total FN-DMC energy is minor, it can become significant in binding energy ($E_{\rm b}$) evaluations of weakly interacting systems. We systematically investigated BSIEs in FN-DMC-based binding energy ($E_{\rm b}$) evaluations using the A24 dataset, a well-known benchmark set of 24 non-covalently bound dimers. Contrary to common expectations, we found that BSIEs in FN-DMC evaluations of $E_{\rm b}$ are indeed significant when small localized basis sets, such as cc-pVDZ, are employed. We observed that BSIEs are larger in dimers with hydrogen-bonding interactions and smaller in dispersion-dominated interactions. We also found that augmenting the basis sets with diffuse orbitals, using counterpoise (CP) correction, or both, effectively mitigates BSIEs.