Geometrical and Electronic Structures of MnS 3 –/0 Clusters from Computational Chemistry and Photoelectron Spectroscopy

2018

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Density functional theory and multiconfigurational CASPT2 and RASPT2 methods are employed to investigate the low-lying states of CoGe ( n = 1-3) clusters. With the RASPT2 approach, the active space is extended to 14 orbitals for CoGe, 17 orbitals for CoGe, and 20 orbitals for CoGe. These active spaces include the 3d, 4s, and 4d of Co and 4p of Ge. The 4d of Co is incorporated into these active spaces in order to account for the important double-shell effect of Co. The structural parameters, vibrational frequencies, and relative energies of the low-lying states of CoGe ( n = 1-3) are reported. The ground states of CoGe ( n = 1-3) are computed to be Φ of linear CoGe, B of cyclic CoGe, and B of cyclic CoGe isomer. The ground states of the neutral clusters are calculated to be Δ of linear CoGe,B of cyclic CoGe, and A″ of tetrahedral CoGe isomer. The calculated adiabatic and vertical detachment energies of the anionic ground states are in agreement with the experimental values as observed in the 266 nm anion photoelectron spectra.

Section: Introductionmentioning

confidence: 99%

The Electronic Structures of CoGe_n^–/0 (n = 1–3) Clusters from Multiconfigurational CASSCF/CASPT2 and RASSCF/RASPT2 Calculations

2018

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“…In such cases, the multiconfigurational CASSCF/CASPT2 method needs to be employed. With the ability to calculate the energies of all of the important ground and excited states with high accuracy, CASSCF/CASPT2 has been known as a sufficient method to investigate the low-lying states of transition metal-containing compounds. − Also, the electron detachment energies of the anionic clusters as computed with the CASPT2 method are usually in good agreement with the experimental values as observed in the photoelectron spectra. − ,− To the best of our knowledge, the multiconfigurational CASSCF/CASPT2 method has not been employed to study the geometrical and electronic structures of vanadium-doped germanium clusters.…”

Section: Introductionmentioning

confidence: 99%

Computational Investigation of the Geometrical and Electronic Structures of VGe_n^–/0 (n = 1–4) Clusters by Density Functional Theory and Multiconfigurational CASSCF/CASPT2 Method

Nguyen

2017

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Density functional theory and the multiconfigurational CASSCF/CASPT2 method have been employed to study the low-lying states of VGe (n = 1-4) clusters. For VGe and VGe clusters, the relative energies and geometrical structures of the low-lying states are reported at the CASSCF/CASPT2 level. For the VGe and VGe clusters, the computational results show that due to the large contribution of the Hartree-Fock exact exchange, the hybrid B3LYP, B3PW91, and PBE0 functionals overestimate the energies of the high-spin states as compared to the pure GGA BP86 and PBE functionals and the CASPT2 method. On the basis of the pure GGA BP86 and PBE functionals and the CASSCF/CASPT2 results, the ground states of anionic and neutral clusters are defined, the relative energies of the excited states are computed, and the electron detachment energies of the anionic clusters are evaluated. The computational results are employed to give new assignments for all features in the photoelectron spectra of VGe and VGe clusters.

“…Because of the open 3d shell of V, VSi 3 –/0 clusters are expected to have complicated geometrical and electronic structures as transition metal containing clusters. In many cases, it is found that several low-lying states are nearly degenerate, and numerous isomers have almost the same stability. ,− Density functional theory is usually used to study vanadium doped silicon clusters due to the low computational cost. , However, in order to obtain all the relevant low-lying states which are useful to interpret the photoelectron spectroscopy, the multireference CASSCF/CASPT2 method needs to be employed. ,,, Furthermore, to evaluate the relative energy order of the mild multireference electronic states, the ROHF/CCSD(T) method is used. ,,,, Despite a single-reference method, the CCSD(T) can give the right relative energy order of the mild multireference electronic states around the minima on the potential energy surfaces. The reason for this feature of the CCSD(T) method is that, around the minima on the potential energy surfaces, dynamical electron correlation is more important than static electron correlation.…”

Section: Introductionmentioning

confidence: 99%

“…7,16 However, in order to obtain all the relevant low-lying states which are useful to interpret the photoelectron spectroscopy, the multireference CASSCF/CASPT2 method needs to be employed. 20,21,25,26 Furthermore, to evaluate the relative energy order of the mild multireference electronic states, the ROHF/ CCSD(T) method is used. 20,22,23,27,28 this feature of the CCSD(T) method is that, around the minima on the potential energy surfaces, dynamical electron correlation is more important than static electron correlation.…”

Section: Introductionmentioning

confidence: 99%

Quantum Chemical Study of the Low-Lying Electronic States of VSi₃^–/0 Clusters and Interpretation of the Anion Photoelectron Spectrum

2016

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The geometrical and electronic structures of VSi3(-/0) clusters have been investigated with the DFT, CCSD(T), and CASSCF/CASPT2 methods. The results showed that the suitable functional to identify the ground states of VSi3(-/0) clusters is not the B3LYP but the BP86. At the BP86, CCSD(T), and CASPT2 levels, the ground state of the anionic cluster was the (1)A' ((1)A1) of tetrahedral η(3)-(Si3)V(-) isomer, while that of the neutral cluster was the 1(2)A' and 1(2)A″ (1(2)E) of the same isomer. The 1(2)A' and 1(2)A″ of the tetrahedral η(3)-(Si3)V isomer were the results of the Jahn-Teller distortions of the 1(2)E in C3v symmetry. All three bands in the photoelectron spectrum of the VSi3(-) cluster were interpreted by one-electron detachments from the (1)A' anionic ground state on the basis of the BP86, CCSD(T), and CASPT2 methods. The calculated adiabatic and vertical detachment energies were in agreement with the experimental values. The broad shape of the first band was explained by Franck-Condon factor simulations for the (1)A' → 1(2)A' and (1)A' → 1(2)A″ transitions within the tetrahedral η(3)-(Si3)V(-/0) isomers.