Matz Florian, Drennhaus Jan Philipp, Ferino-Pérez Anthuan, Jagau Thomas-C
Department of Chemistry, KU Leuven, B-3001 Leuven, Belgium.
J Chem Phys. 2025 Sep 14;163(10). doi: 10.1063/5.0279034.
We model Auger spectra using second-order Møller-Plesset perturbation (MP2) theory combined with complex-scaled basis functions. For this purpose, we decompose the complex MP2 energy of the core-hole state into contributions from specific decay channels and propose a corresponding equation-of-motion (EOM) method for computing the doubly ionized final states of Auger decay. These methods lead to significant savings in computational cost compared to our recently developed approaches based on coupled-cluster theory [F. Matz and T.-C. Jagau, J. Chem. Phys. 156, 114117 (2022)]. The test set for this study comprises water, ammonia, methane, hydrogen sulfide, phosphine, and silane. The energies of the final states of Auger decay are obtained with an accuracy comparable to EOM coupled-cluster singles and doubles (CCSD) theory. Partial decay widths and branching ratios between KLL, KLM, and KMM decay of K-shell holes in third-row hydrides are in good agreement with EOM-CCSD, while deviations are more significant for second-row hydrides. For L1-shell holes, which undergo Coster-Kronig decay, MP2 yields unphysical results. However, we show that a suitable shift of the MP2 energy denominators leads to more reliable branching ratios and spectra for these problematic cases.
我们使用二阶莫勒-普列斯特定则微扰（MP2）理论结合复标度基函数对俄歇光谱进行建模。为此，我们将芯孔态的复MP2能量分解为特定衰变通道的贡献，并提出了一种相应的运动方程（EOM）方法来计算俄歇衰变的双电离末态。与我们最近基于耦合簇理论开发的方法[F. Matz和T.-C. Jagau，《化学物理杂志》156, 114117 (2022)]相比，这些方法显著节省了计算成本。本研究的测试集包括水、氨、甲烷、硫化氢、磷化氢和硅烷。俄歇衰变末态的能量以与运动方程耦合簇单双激发（CCSD）理论相当的精度获得。第三周期氢化物中K壳层空穴的KLL、KLM和KMM衰变之间的部分衰变宽度和分支比与EOM-CCSD结果吻合良好，而对于第二周期氢化物，偏差更为显著。对于经历科斯特-克罗尼格衰变的L1壳层空穴，MP2给出了不符合实际的结果。然而，我们表明，对MP2能量分母进行适当的偏移会为这些有问题的情况带来更可靠的分支比和光谱。
