Influence of pseudopotentials on excitation energies from selected configuration interaction and diffusion Monte Carlo
Influence of pseudopotentials on excitation energies from selected configuration interaction and diffusion Monte Carlo
复制标题
选定构型相互作用和扩散蒙特卡罗赝势对激发能的影响
DOI：
10.1016/j.rechem.2019.100002
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发表时间：
2019
影响因子：
2.3
通讯作者：
Pierre‐François Loos
中科院分区：
文献类型：
--
作者：
A. Scemama;M. Caffarel;A. Benali;D. Jacquemin;Pierre‐François Loos
由于激发态的多样性，电子结构理论方法中激发态的忠实描述仍然是现代理论化学的巨大挑战之一。量子蒙特卡罗 (QMC) 方法已非常成功地应用于基态性质的研究，但对于电子激发态的研究仍然普遍不如其他非随机方法有效。尽管如此，我们最近报告了在 Jastrow-free QMC 协议中固定节点扩散蒙特卡罗 (FN-DMC) 上小有机分子的精确激发能量，该协议依赖于使用称为 CIPSI（使用迭代进行扰动选择的配置交互）的选定配置交互 (sCI) 算法对节点表面进行确定性和系统性构建。尽管精度很高，但由于核心电子的存在，这些全电子计算的计算成本很高。从 QMC 模拟中去除这些化学惰性电子的一种非常流行的方法是引入赝势（也称为有效核心势）。以水分子为例，我们研究了 Burkatzki-Filippi-Dolg (BFD) 赝势及其相关基组对 sCI 和 FN-DMC 方法获得的垂直激发能的影响。尽管已知这些赝势对于基态特性来说相对安全，但我们证明，如果追求高精度的垂直跃迁能量，可能需要特别小心。事实上，通过比较全电子和仅化合价计算，我们表明使用赝势和相关基组可以在激发能上引起 0.05eV 量级的差异。幸运的是，可以在 sCI 水平上对这种转变进行合理的估计。
Due to their diverse nature, the faithful description of excited states within electronic structure theory methods remains one of the grand challenges of modern theoretical chemistry. Quantum Monte Carlo (QMC) methods have been applied very successfully to ground state properties but still remain generally less effective than other non-stochastic methods for electronically excited states. Nonetheless, we have recently reported accurate excitation energies for small organic molecules at the fixed-node diffusion Monte Carlo (FN-DMC) within a Jastrow-free QMC protocol relying on a deterministic and systematic construction of nodal surfaces using the selected configuration interaction (sCI) algorithm known as CIPSI (Configuration Interaction using a Perturbative Selection made Iteratively). Albeit highly accurate, these all-electron calculations are computationally expensive due to the presence of core electrons. One very popular approach to remove these chemically-inert electrons from the QMC simulation is to introduce pseudopotentials (also known as effective core potentials). Taking the water molecule as an example, we investigate the influence of Burkatzki-Filippi-Dolg (BFD) pseudopotentials and their associated basis sets on vertical excitation energies obtained with sCI and FN-DMC methods. Although these pseudopotentials are known to be relatively safe for ground state properties, we evidence that special care may be required if one strives for highly accurate vertical transition energies. Indeed, comparing all-electron and valence-only calculations, we show that using pseudopotentials with the associated basis sets can induce differences of the order of 0.05 eV on the excitation energies. Fortunately, a reasonable estimate of this shift can be estimated at the sCI level.
影响因子：
5.7
作者：
Ambrosetti, Alberto;Alfe, Dario;Tkatchenko, Alexandre
通讯作者：
Tkatchenko, Alexandre