Rudshteyn Benjamin, Weber John L, Coskun Dilek, Devlaminck Pierre A, Zhang Shiwei, Reichman David R, Shee James, Friesner Richard A
Department of Chemistry, Columbia University, 3000 Broadway, New York, New York 10027, United States.
Center for Computational Quantum Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, United States.
J Chem Theory Comput. 2022 May 10;18(5):2845-2862. doi: 10.1021/acs.jctc.1c01071. Epub 2022 Apr 4.
The accurate prediction of ionization energies is essential to understanding the electrochemistry of transition metal complexes in both materials science and biological applications. However, such predictions have been complicated by the scarcity of gas phase experimental data, the relatively large size of the relevant molecules, and the presence of strong electron correlation effects. In this work, we apply all-electron phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) utilizing multideterminant trial wave functions to six metallocene complexes to compare the computed adiabatic and vertical ionization energies with experimental results. We find that ph-AFQMC yields mean absolute errors (MAEs) of 1.69 ± 1.02 kcal/mol for the adiabatic energies and 2.85 ± 1.13 kcal/mol for the vertical energies. We also carry out density functional theory (DFT) calculations using a variety of functionals, which yields MAEs of 3.62-6.98 kcal/mol and 3.31-9.88 kcal/mol, as well as one variant of localized coupled cluster calculations (DLPNO-CCSD(T) with moderate PNO cutoffs), which has MAEs of 4.96 and 6.08 kcal/mol, respectively. We also test the reliability of DLPNO-CCSD(T) and DFT on acetylacetonate (acac) complexes for adiabatic energies measured in the same manner experimentally, and we find higher MAEs, ranging from 4.56 to 10.99 kcal/mol (with a different ordering) for DFT and 6.97 kcal/mol for DLPNO-CCSD(T). Finally, by utilizing experimental solvation energies, we show that accurate reduction potentials in solution for the metallocene series can be obtained from the AFQMC gas phase results.
准确预测电离能对于理解过渡金属配合物在材料科学和生物应用中的电化学性质至关重要。然而，由于气相实验数据稀缺、相关分子尺寸相对较大以及存在强电子关联效应，此类预测变得复杂。在这项工作中，我们将利用多行列式试探波函数的全电子无相辅助场量子蒙特卡罗方法（ph-AFQMC）应用于六种茂金属配合物，以将计算得到的绝热和垂直电离能与实验结果进行比较。我们发现，ph-AFQMC对于绝热能量的平均绝对误差（MAE）为1.69±1.02 kcal/mol，对于垂直能量的平均绝对误差为2.85±1.13 kcal/mol。我们还使用多种泛函进行密度泛函理论（DFT）计算，其平均绝对误差为3.62 - 6.98 kcal/mol和3.31 - 9.88 kcal/mol，以及一种局部耦合簇计算变体（具有中等PNO截断的DLPNO-CCSD(T)），其平均绝对误差分别为4.96和6.08 kcal/mol。我们还以相同的实验方式测试了DLPNO-CCSD(T)和DFT对乙酰丙酮（acac）配合物绝热能量的可靠性，我们发现对于DFT，平均绝对误差更高，范围为4.56至10.99 kcal/mol（顺序不同），对于DLPNO-CCSD(T)为6.97 kcal/mol。最后，通过利用实验溶剂化能，我们表明可以从AFQMC气相结果获得茂金属系列在溶液中的准确还原电位。
