本文采用实空间扩散蒙特卡罗（DMC）方法研究了二氢化铍（BeH $_2$）和乙炔（C $_2$ H $_2$）分子。分子作为也许是最简单的原型，说明了困难的偏见，在固定节点DMC计算，可能会出现与使用有效的核心潜力（ECP）或其他非本地运营商。这对于最近引入的用于$2s2p$元素的相关一致ECP（ccECP）尤其相关。相应的ccECP由于对全电子对应物的更高保真度而表现出更深的势函数，这可能导致更大的局部能量波动。我们指出，困难源于问题，是直接解决的升级基组，使用T-移动的非本地条款，包括一些配置到审判功能和类似的。所得准确度对应于ccECP目标（化学准确度），并且与独立相关计算一致。进一步的可能性升级的DMC算法的可靠性和更好地适应和更强大的Jastrow因素的考虑进行了讨论。
英文摘要：
We study beryllium dihydride (BeH$_2$) and acetylene (C$_2$H$_2$) molecules using real-space diffusion Monte Carlo (DMC) method. The molecules serve as perhaps the simplest prototypes that illustrate the difficulties with biases in the fixed-node DMC calculations that might appear with the use of effective core potentials (ECPs) or other nonlocal operators. This is especially relevant for the recently introduced correlation consistent ECPs (ccECPs) for $2s2p$ elements. Corresponding ccECPs exhibit deeper potential functions due to higher fidelity to all-electron counterparts, which could lead to larger local energy fluctuations. We point out that the difficulties stem from issues that are straightforward to address by upgrades of basis sets, use of T-moves for nonlocal terms, inclusion of a few configurations into the trial function and similar. The resulting accuracy corresponds to the ccECP target (chemical accuracy) and it is in consistent agreement with independent correlated calculations. Further possibilities for upgrading the reliability of the DMC algorithm and considerations for better adapted and more robust Jastrow factors are discussed as well.
Exchange Monte Carlo for continuous-space Path Integral Monte Carlo simulation
The University of Tokyo（东京大学）；Institute for Physics of Intelligence, The University of Tokyo（东京大学物理智能研究所）；Institute for Solid State Physics, The University of Tokyo（东京大学固体物理研究所）
