Lifetimes of Be 3 2– and Mg 3 2– Cluster Dianions
Lifetimes of Be 3 2– and Mg 3 2– Cluster Dianions
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Be 3 2– 和 Mg 3 2– 簇二阴离子的寿命
DOI：
10.1021/acs.jpca.1c00770
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Sommerfeld, Thomas
中科院分区：
文献类型：
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作者：
Davis, Jeremy U.;Phung, Quan Manh;Yanai, Takeshi;Ehara, Masahiro;Sommerfeld, Thomas
碱土金属三聚体簇二价阴离子Be 32-和Mg 32-位于其各自的一价阴离子上方，因此可以通过电子自动脱离而衰变。因此，这些二价阴离子只具有短暂的共振态，在这里，我们研究这些状态使用正则化解析延拓以及复杂的吸收势结合各种量子化学方法，包括CCSD（T），SACCI，EOM-CCSD，CASPT 2，和NEVPT 2。对于Be ~（32）-和Mg ~（32）-，在两个最低的p−σ和p−π轨道上，分别发现了对应于两个过剩电子不同占据模式的四个低能共振态：两个态以双占据构型为主，表现出σ和π芳族特征。另外两种状态对应于开壳层单线态/三线态对。所有的二价阴离子态都被发现是高度不稳定的，并且具有短的寿命：它们显示出在其各自的一价阴离子的基态以上的2.3-4.3 eV的能量范围内的共振位置，以及在1和1.5 eV之间的宽宽度转换成飞秒寿命。对于Be 32-和Mg 32-，四种状态之间的差异很小，但三重态往往比三个单重态略稳定。因此，在多电荷离子的情况下，多余电子的芳香性需要第二阶段，而库仑排斥需要前面和中心。除了两个孤立的簇二价阴离子，模型稳定的小水簇进行了探索。我们的研究结果表明，共振位置和宽度的急剧下降对应的寿命增加了2个数量级。然而，“溶剂化”簇仍然是共振的，并且将需要例如更大的水簇或提供更大的键偶极的配体环境的更显著的扰动来完全稳定位于小系统（例如碱金属三聚体）上的两个过量电子。
The alkaline earth metal trimer cluster dianions Be32–and Mg32–lie energetically above their respective monoanions and can therefore decay by electron autodetachment. Consequently, these dianions possess only short-lived resonance states, and here we study these states using regularized analytic continuation as well as complex absorbing potentials combined with a wide a variety of quantum chemistry methods including CCSD(T), SACCI, EOM-CCSD, CASPT2, and NEVPT2. For both Be32–and Mg32–, four low-energy resonance states corresponding to different occupation patterns of the two excess electrons in the two lowest p−σ and p−π orbitals are identified: Two states are dominated by doubly occupied configurations and can be characterized as showing σ and π aromatic character. The other two states correspond to the open-shell singlet/triplet pair. All dianion states are found to be highly unstable and to possess short lifetimes: They show resonance positions in the energy range 2.3–4.3 eV above the ground states of their respective monoanions and broad widths between 1 and 1.5 eV translating into femtosecond lifetimes. For both Be32–and Mg32–, the differences between the four states are small, but the triplet states tend to be slightly more stable than the three singlet states. Thus, in the case of the multicharged ion aromatic character of the excess electrons takes second stage while Coulomb repulsion takes front and center. In addition to the two isolated cluster dianions, model stabilization by small water clusters is explored. Our results show a dramatic drop in resonance position and width corresponding to a lifetime increase by 2 orders of magnitude. However, the “solvated” clusters are still resonances, and a more pronounced perturbation by, for example, yet larger water clusters or a ligand environment providing larger bond dipoles will be needed to fully stabilize two excess electrons localized on a small system such as an alkaline metal trimer.