Department of Chemistry and Cherry Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA.
J Chem Phys. 2023 Mar 28;158(12):124112. doi: 10.1063/5.0137096.
This work examines the accuracy and precision of x-ray absorption spectra computed with a multireference approach that combines generalized active space (GAS) references with the driven similarity renormalization group (DSRG). We employ the x-ray absorption benchmark of organic molecule (XABOOM) set, consisting of 116 transitions from mostly organic molecules [Fransson et al., J. Chem. Theory Comput. 17, 1618 (2021)]. Several approximations to a full-valence active space are examined and benchmarked. Absolute excitation energies and intensities computed with the GAS-DSRG truncated to second-order in perturbation theory are found to systematically underestimate experimental and reference theoretical values. Third-order perturbative corrections significantly improve the accuracy of GAS-DSRG absolute excitation energies, bringing the mean absolute deviation from experimental values down to 0.32 eV. The ozone molecule and glyoxylic acid are particularly challenging for second-order perturbation theory and are examined in detail to assess the importance of active space truncation and intruder states.
这项工作研究了使用多参考方法计算的 X 射线吸收谱的准确性和精密度，该方法结合了广义活性空间（GAS）参考和驱动相似性重整化群（DSRG）。我们采用了由有机分子组成的 X 射线吸收基准（XABOOM）集，其中包含 116 个跃迁[Fransson 等人，J. Chem. Theory Comput. 17, 1618 (2021)]。我们研究并基准了几种全价活性空间的近似方法。在微扰理论中截断到二阶的 GAS-DSRG 计算得到的绝对激发能和强度被发现系统地低估了实验值和参考理论值。三阶微扰修正显著提高了 GAS-DSRG 绝对激发能的准确性，使与实验值的平均绝对偏差降低至 0.32 eV。臭氧分子和乙醛酸对于二阶微扰理论特别具有挑战性，我们对其进行了详细研究，以评估活性空间截断和闯入态的重要性。
