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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Assignment of the photoelectron spectra of FeS _3 - by density functional theory, CASPT2, and RCCSD(T) calculations
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Assignment of the photoelectron spectra of FeS _3 - by density functional theory, CASPT2, and RCCSD(T) calculations

机译：用密度泛函理论，CASPT2和RCCSD（T）计算分配FeS _3-的光电子能谱

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摘要

The geometric structures of FeS _3 and FeS _3 - with spin multiplicities ranging from singlet to octet were optimized at the B3LYP level, allowing two low-lying conformations for these clusters to be identified. The planar D _(3h) conformation contains three S ~(2-) atomic ligands (S _3Fe ~(0/-)), whereas the C _(2v) structure contains, in addition to an atomic S ~(2-) ligand, also a S _2 ~(2-) ligand that is side-on-bound to the iron cation: an η ~2-S _2FeS conformation. Subsequently, energy differences between the various states of these conformations were estimated by carrying out geometry optimizations at the multireference CASPT2 level. Several competing structures for the ground state of the anionic cluster were recognized at this level. Relative stabilities were also estimated by performing single-point RCSSD(T) calculations on the B3LYP geometries. The ground state of the neutral complex was unambiguously found to be ~5B _2. The ground state of the anion is considerably less certain. The 1 ~4B _2, 2 ~4B _2, ~4B _1, and ~6A _1 states were all found as low-lying η ~2-S _2FeS - states. Also, ~4B _2 of S _3Fe - has a comparable CASPT2 energy. In contrast, B3LYP and RCCSD(T) mutually agree that the S _3Fe - state is at a much higher energy. Energetically, the bands of the photoelectron spectra of FeS 3 - are reproduced at the CASPT2 level as ionizations from either the ~4B _2 or ~6A _1 state of η ~2-S _2FeS. However, the Franck-Condon factors obtained from a harmonic vibrational analysis at the B3LYP level show that only the ~4B _2-to- ~5B _2 ionization, which preserves the η ~2-S _2Fe-S conformation, provides the best vibrational progression match with the X band of the experimental photoelectron spectra.
机译：FeS _3和FeS _3-的自旋多重性从单峰到八位位点的几何结构在B3LYP级别上得到优化，从而可以识别出这些簇的两个低洼构象。平面D _（3h）构象包含三个S〜（2-）原子配体（S _3Fe〜（0 /-）），而C _（2v）结构除原子S〜（2-）外还包含配体，也是与铁阳离子侧键结合的S _2〜（2-）配体：η〜2-S _2FeS构象。随后，通过在多参考CASPT2级别上进行几何优化来估算这些构型的各种状态之间的能量差。在这一水平上，阴离子簇的基态有几种竞争结构。还可以通过对B3LYP几何形状执行单点RCSSD（T）计算来估计相对稳定性。明确发现中性络合物的基态为〜5B _2。阴离子的基态非常不确定。发现1〜4B _2、2〜4B _2，〜4B _1和〜6A _1状态均为低地η〜2-S _2FeS-状态。同样，S _3Fe的〜4B _2具有可比的CASPT2能量。相反，B3LYP和RCCSD（T）相互同意S _3Fe-态的能量要高得多。从能量上讲，FeS 3-的光电子能谱在CASPT2能级上作为电离从η〜2-S _2FeS的〜4B _2或〜6A _1状态重现。但是，从B3LYP水平的谐波振动分析获得的Franck-Condon因子显示，只有〜4B _2- ~~ 5B _2电离能保留η〜2-S _2Fe-S构象，提供了最佳的振动进程与实验光电子谱的X谱带匹配。

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