Department of Chemistry, Washington State University, Pullman, Washington 99164-4630, USA.
Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA.
J Chem Phys. 2018 Jun 21;148(23):234308. doi: 10.1063/1.5037346.
Theoretical predictions of the three lowest adiabatic and vertical ionization potentials of water were obtained from the Feller-Peterson-Dixon approach. This approach combines multiple levels of coupled cluster theory with basis sets as large as aug-cc-pV8Z in some cases and various corrections up to and including full configuration interaction theory. While agreement with experiment for the adiabatic ionization potential of the lowest energy B state was excellent, differences for other states were much larger, sometimes exceeding 10 kcal/mol (0.43 eV). Errors of this magnitude are inconsistent with previous benchmark work on 52 adiabatic ionization potentials, where a root mean square of 0.20 kcal/mol (0.009 eV) was found. Difficulties in direct comparisons between theory and experiment for vertical ionization potentials are discussed. With regard to the differences found for the A/Π and B adiabatic ionization potentials, a reinterpretation of the experimental spectrum appears justified.
从 Feller-Peterson-Dixon 方法得到了水的三个最低绝热和垂直电离势的理论预测。该方法将耦合簇理论的多个水平与基组结合在一起，在某些情况下，基组大到 aug-cc-pV8Z，并包含直至全组态相互作用理论的各种校正。虽然对于最低能量 B 态的绝热电离势与实验结果非常吻合，但其他态的差异要大得多，有时超过 10 千卡/摩尔（0.43eV）。这种量级的误差与之前对 52 个绝热电离势的基准工作不一致，其中发现均方根误差为 0.20 千卡/摩尔（0.009eV）。讨论了理论和实验之间垂直电离势直接比较的困难。对于 A/Π 和 B 绝热电离势的差异，对实验光谱进行重新解释似乎是合理的。
