Hao Hongxia, Shee James, Upadhyay Shiv, Ataca Can, Jordan Kenneth D, Rubenstein Brenda M
Department of Chemistry , Brown University , Providence , Rhode Island 02912 , United States.
Department of Chemistry , Columbia University , New York , New York 10027 , United States.
J Phys Chem Lett. 2018 Nov 1;9(21):6185-6190. doi: 10.1021/acs.jpclett.8b02733. Epub 2018 Oct 15.
Neutral molecules with sufficiently large dipole moments can bind electrons in diffuse nonvalence orbitals with most of their charge density far from the nuclei, forming so-called dipole-bound anions. Because long-range correlation effects play an important role in the binding of an excess electron and overall binding energies are often only on the order of 10s-100s of wave numbers, predictively modeling dipole-bound anions remains a challenge. Here, we demonstrate that quantum Monte Carlo methods can accurately characterize molecular dipole-bound anions with near-threshold dipole moments. We also show that correlated sampling Auxiliary Field Quantum Monte Carlo is particularly well-suited for resolving the fine energy differences between the neutral and anionic species. These results shed light on the fundamental limitations of quantum Monte Carlo methods and pave the way toward using them for the study of weakly bound species that are too large to model using traditional electron structure methods.
具有足够大偶极矩的中性分子能够在离核较远且电荷密度大部分分布在其中的弥散非价轨道中束缚电子，从而形成所谓的偶极束缚阴离子。由于长程关联效应在多余电子的束缚过程中起着重要作用，且整体束缚能通常仅在几十到几百波数的量级，因此对偶极束缚阴离子进行预测性建模仍然是一项挑战。在此，我们证明量子蒙特卡罗方法能够精确地表征具有近阈值偶极矩的分子偶极束缚阴离子。我们还表明，相关采样辅助场量子蒙特卡罗方法特别适合于解析中性和阴离子物种之间的细微能量差异。这些结果揭示了量子蒙特卡罗方法的基本局限性，并为将其用于研究因尺寸太大而无法用传统电子结构方法建模的弱束缚物种铺平了道路。
