The Complete‐Active‐Space Self‐Consistent‐Field Approach and Its Application to Molecular Complexes of the f‐Elements

Kerridge, Andrew

doi:10.1002/9781118688304.ch5

Cited by 12 publications

(14 citation statements)

References 43 publications

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“…However, the overall temperature dependence of χ M T in the 2–150 K range as well as the magnetization curve at 2 K for magnetic fields stronger than 5 kOe are not well reproduced (Figures S19 and S20), suggesting that the eigenvectors and eigenvalues calculated ab initio are not in good agreement with the microstates of the J = 15/2 ground state manifold of Er . It is noteworthy that similar discrepancies between experimental and ab initio CASSCF-calculated low-temperature χ M T values and magnetization isotherms have been reported for other Er III compounds. , These discrepancies appear to be particular for Er III among the trivalent lanthanoid ions and could be due to the limited size of the atomic basis set for Er III or to a contribution of dynamical electron correlation that is not accounted for in CASSCF/RASSI calculations. , …”

Section: Resultsmentioning

confidence: 55%

“…34,83 These discrepancies appear to be particular for Er III among the trivalent lanthanoid ions and could be due to the limited size of the atomic basis set for Er III or to a contribution of dynamical electron correlation that is not accounted for in CASSCF/RASSI calculations. 43,84 Utilizing an alternative CF approach, a satisfactory rationalization of the INS transitions observed for Er D can be achieved by fitting the experimental INS data to the parameters of a simplified CF Hamiltonian based on extended Stevens operators. 68 The fitting of the experimental INS data was carried out using as a background the phonon spectra of Y D collected at 10 and 50 K (Figure S16) with the Y D data at 10 K scaled to match the intensity of the phonon region in Er D at 5 K. On the basis of a purely axial CF Hamiltonian (eq 2) it is not possible to rationalize the observed INS peaks.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study

et al. 2016

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Inelastic neutron scattering (INS) has been used to investigate the crystal field (CF) magnetic excitations of the analogs of the most representative lanthanoid-polyoxometalate single-molecule magnet family: Na[Ln(WO)] (Ln = Nd, Tb, Ho, Er). Ab initio complete active space self-consistent field/restricted active space state interaction calculations, extended also to the Dy analog, show good agreement with the experimentally determined low-lying CF levels, with accuracy better in most cases than that reported for approaches based only on simultaneous fitting to CF models of magnetic or spectroscopic data for isostructural Ln families. In this work we demonstrate the power of a combined spectroscopic and computational approach. Inelastic neutron scattering has provided direct access to CF levels, which together with the magnetometry data, were employed to benchmark the ab initio results. The ab initio determined wave functions corresponding to the CF levels were in turn employed to assign the INS transitions allowed by selection rules and interpret the observed relative intensities of the INS peaks. Ultimately, we have been able to establish the relationship between the wave function composition of the CF split Ln ground multiplets and the experimentally measured magnetic and spectroscopic properties for the various analogs of the Na[Ln(WO)] family.

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Section: Resultsmentioning

confidence: 55%

Section: ■ Results and Discussionmentioning

confidence: 99%

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study

et al. 2016

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“…These metals were selected for two reasons. First, many studies have concluded that the covalent contribution to bonding in the actinide series peaks at either U or Pu. , Second, cerium is commonly used as a nonradioactive analogue for plutonium. Thus, understanding how it differs from actinides is crucial for detailing how 4f and 5f elements diverge in terms of their electronic structures. , …”

Section: Introductionmentioning

confidence: 99%

Computational Investigation of the Bonding in [(η⁵–Cp′)₃(η¹–Cp′)M]^1– (M = Pu, U, Ce)

2021

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displays a significantly longer η 1 −Cp′ distance in the solid state compared to the U 3+ and Pu 3+ analogues. To better understand this observation, a theoretical investigation was undertaken to examine the differences in bonding between the actinides 1-Pu and 1-U and how they compare with 1-Ce. The results show that although the bonding is largely ionic and dominated by ligand (2p)−metal (6d/ 5d) interactions, the polarization of 5f orbitals plays a significant role for 1-Pu and 1-U compared to the 4f-orbitals of 1-Ce. The lack of Ce(4f) interactions is compensated for by increased participation of the Ce(5d) orbitals relative to the actinide 6d orbitals, particularly for the σ-bound η 1 −Cp′ ligand. The use of multiple theoretical approaches including topological, localization, and energy decomposition approaches shows that 1-Pu and 1-U are very similar in covalent character compared to 1-Ce, though the composition and energy of the different interactions suggest that 1-U presents the strongest overall interactions.

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“…The proper selection of this active space is crucial to obtain reliable multiconfigurational wave functions and corresponding energies. Unfortunately, this delicate selection is mostly achieved by tedious trial-and-error procedures, [23][24][25] several empirical guidelines, 19,23,26,27 and chemical intuition, 23,25,28,29 a term that lacks a clear definition in this context. Obviously, this is a not at all satisfactory situation for a highly advanced ab initio method.…”

Section: Introductionmentioning

confidence: 99%

autoCAS: A Program for Fully Automated Multiconfigurational Calculations

Stein

Reiher

2019

J Comput Chem

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We present our implementation AUTOCAS for fully automated multiconfigurational calculations, which we also make available free of charge on our webpages. The graphical user interface of AUTOCAS connects a general electronic structure program with a density-matrix renormalization group program to carry out our recently introduced automated active space selection protocol for multiconfigurational calculations Reiher, J. Chem. Theory Comput., 2016, 12, 1760). Next to this active space selection, AUTOCAS carries out several steps of multiconfigurational calculations so that only a minimal input is required to start them, comparable to that of a standard Kohn-Sham density-functional theory calculation, so that black-box multiconfigurational calculations become feasible. Furthermore, we introduce a new extension to the selection algorithm that facilitates automated selections for molecules with large valence orbital spaces consisting of several hundred orbitals.

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The Complete‐Active‐Space Self‐Consistent‐Field Approach and Its Application to Molecular Complexes of the f‐Elements

Cited by 12 publications

References 43 publications

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study

Computational Investigation of the Bonding in [(η⁵–Cp′)₃(η¹–Cp′)M]^1– (M = Pu, U, Ce)

autoCAS: A Program for Fully Automated Multiconfigurational Calculations

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The Complete‐Active‐Space Self‐Consistent‐Field Approach and Its Application to Molecular Complexes of the f‐Elements

Cited by 12 publications

References 43 publications

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study

Computational Investigation of the Bonding in [(η5–Cp′)3(η1–Cp′)M]1– (M = Pu, U, Ce)

autoCAS: A Program for Fully Automated Multiconfigurational Calculations

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Computational Investigation of the Bonding in [(η⁵–Cp′)₃(η¹–Cp′)M]^1– (M = Pu, U, Ce)