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Thomas E. Albrecht-schmitt - One of the best experts on this subject based on the ideXlab platform.

  • Directed evolution of the periodic table: probing the electronic structure of late Actinides
    Dalton transactions (Cambridge England : 2003), 2017
    Co-Authors: Matthew L. Marsh, Thomas E. Albrecht-schmitt
    Abstract:

    Recent investigations of the coordination chemistry and physical properties of berkelium (Z = 97) and californium (Z = 98) have revealed fundamental differences between post-curium elements and lighter members of the Actinide Series. This review highlights these developments and chronicles key findings and concepts from the last half-century that have helped usher in a new understanding of the evolution of electronic structure in the periodic table.

  • Fleeting glimpse of an elusive element
    Nature, 2016
    Co-Authors: Thomas E. Albrecht-schmitt
    Abstract:

    A heroic effort to characterize the chemistry of actinium, a short-lived radioactive element, reveals surprising differences in behaviour compared with other elements in the Actinide Series.

  • Inorganic chemistry: Fleeting glimpse of an elusive element
    Nature, 2016
    Co-Authors: Thomas E. Albrecht-schmitt
    Abstract:

    A heroic effort to characterize the chemistry of actinium, a short-lived radioactive element, reveals surprising differences in behaviour compared with other elements in the Actinide Series.

  • Evaluation of f -element borate chemistry
    Coordination Chemistry Reviews, 2016
    Co-Authors: Mark A. Silver, Thomas E. Albrecht-schmitt
    Abstract:

    Abstract The synthesis, structure elucidation, and spectroscopic measurements of a myriad of new, f-element borates has revealed the unusual effects that this electron-rich oxoanion has on the electronic properties of lanthanides and Actinides. One purpose of these studies was to provide models for Actinide compounds that may exist in either vitrified nuclear waste or in repositories located within salt deposits that have significant borate content. In addition, the radiation-damage resilience of polyborate networks positions these materials as suitable candidates for probing coordination chemistry and physical properties much deeper into the Actinide Series than is normally possible, and compounds with Actinides up to californium (Z = 98) have been successfully prepared and characterized in exquisite detail. Structural determination of these materials show that both the lanthanide and Actinide Series display previously unknown coordination chemistry, but, more importantly, that the two Series have little overlap in terms of structure and composition, and have few parallels. In addition, some of these compounds display unique physico-chemical properties, one example of which is the selective trapping of radionuclides. The foremost discovery first identified in Actinide borates is that the chemistry of californium represents an onset of unprecedented chemical behavior that compares better with high-oxidation state, early transition metal complexes than it does with earlier f-elements.

  • Oxoanion systems containing trivalent Actinides
    Coordination Chemistry Reviews, 2013
    Co-Authors: Matthew J. Polinski, Eric M. Villa, Thomas E. Albrecht-schmitt
    Abstract:

    Abstract A review of trivalent Actinide oxoanion compounds is presented. This work focuses on the systematics and periodic trends in the trivalent Actinide Series from Pu(III) to Cf(III). Three systems, are focused on: iodates, phosphites, and borates. In the first two Series, the structure and bonding parallels that of lanthanides; whereas in the final Series the chemistry of the Actinides is distinct from the lanthanides.

Nikolas Kaltsoyannis - One of the best experts on this subject based on the ideXlab platform.

  • Quantum chemical topology and natural bond orbital analysis of M-O covalency in M(OC6H5)4 (M = Ti, Zr, Hf, Ce, Th, Pa, U, Np).
    Physical chemistry chemical physics : PCCP, 2020
    Co-Authors: Victoria E. J. Berryman, Jacob J. Shephard, Tatsumi Ochiai, Amy N. Price, Polly L. Arnold, Simon Parsons, Nikolas Kaltsoyannis
    Abstract:

    Covalency is complex yet central to our understanding of chemical bonding, particularly in the Actinide Series. Here we assess covalency in a Series of isostructural d and f transition element compounds M(OC6H5)4 (M = Ti, Zr, Hf, Ce, Th, Pa, U, Np) using scalar relativistic hybrid density functional theory in conjunction with the Natural Bond Orbital (NBO), quantum theory of atoms in molecules (QTAIM) and interacting quantum atoms (IQA) approaches. The IQA exchange–correlation covalency metric is evaluated for the first time for Actinides other than uranium, in order to assess its applicability in the 5f Series. It is found to have excellent correlation with NBO and QTAIM covalency metrics, making it a promising addition to the computational toolkit for analysing metal–ligand bonding. Our range of metrics agree that the Actinide-oxygen bonds are the most covalent of the elements studied, with those of the heavier group 4 elements the least. Within the early Actinide Series, Th stands apart from the other three elements considered, being consistently the least covalent.

  • Transuranic Computational Chemistry
    Chemistry (Weinheim an der Bergstrasse Germany), 2017
    Co-Authors: Nikolas Kaltsoyannis
    Abstract:

    Recent developments in the chemistry of the transuranic elements are surveyed, with particular emphasis on computational contributions. Examples are drawn from molecular coordination and organometallic chemistry, and from the study of extended solid systems. The role of the metal valence orbitals in covalent bonding is a particular focus, especially the consequences of the stabilization of the 5f orbitals as the Actinide Series is traversed. The fledgling chemistry of transuranic elements in the +II oxidation state is highlighted. Throughout, the symbiotic interplay of experimental and computational studies is emphasized; the extraordinary challenges of experimental transuranic chemistry afford computational chemistry a particularly valuable role at the frontier of the periodic table.

  • Bonding Trends Traversing the Tetravalent Actinide Series: Synthesis, Structural, and Computational Analysis of AnIV(Aracnac)4 Complexes (An = Th, U, Np, Pu; Aracnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-tBu2C6H3)
    Inorganic chemistry, 2012
    Co-Authors: David D. Schnaars, Nikolas Kaltsoyannis, Andrew J. Gaunt, Trevor W. Hayton, Matthew B. Jones, Ian Kirker, Iain May, Sean D. Reilly, Brian L. Scott
    Abstract:

    A Series of tetravalent An(IV) complexes with a bis-phenyl β-ketoiminate N,O donor ligand has been synthesized with the aim of identifying bonding trends and changes across the Actinide Series. The neutral molecules are homoleptic with the formula An(Aracnac)4 (An = Th (1), U (2), Np (3), Pu (4); Aracnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-tBu2C6H3) and were synthesized through salt metathesis reactions with Actinide chloride precursors. NMR and electronic absorption spectroscopy confirm the purity of all four new compounds and demonstrate stability in both solution and the solid state. The Th, U, and Pu complexes were structurally elucidated by single-crystal X-ray diffraction and shown to be isostructural in space group C2/c. Analysis of the bond lengths reveals shortening of the An–O and An–N distances arising from the Actinide contraction upon moving from 1 to 2. The shortening is more pronounced upon moving from 2 to 4, and the steric constraints of the tetrakis complexes appear to prevent the enhanced U–O ...

  • Does covalency increase or decrease across the Actinide Series? Implications for minor Actinide partitioning.
    Inorganic chemistry, 2012
    Co-Authors: Nikolas Kaltsoyannis
    Abstract:

    A covalent chemical bond carries the connotation of overlap of atomic orbitals between bonded atoms, leading to a buildup of the electron density in the internuclear region. Stabilization of the valence 5f orbitals as the Actinide Series is crossed leads, in compounds of the minor Actinides americium and curium, to their becoming approximately degenerate with the highest occupied ligand levels and hence to the unusual situation in which the resultant valence molecular orbitals have significant contributions from both Actinide and the ligand yet in which there is little atomic orbital overlap. In such cases, the traditional quantum-chemical tools for assessing the covalency, e.g., population analysis and spin densities, predict significant metal–ligand covalency, although whether this orbital mixing is really covalency in the generally accepted chemical view is an interesting question. This review discusses our recent analyses of the bonding in AnCp3 and AnCp4 (An = Th–Cm; Cp = η5-C5H5) using both the trad...

  • does covalency really increase across the 5f Series a comparison of molecular orbital natural population spin and electron density analyses of ancp 3 an th cm cp eta 5 c5h5
    Dalton Transactions, 2011
    Co-Authors: Ian Kirker, Nikolas Kaltsoyannis
    Abstract:

    The title compounds are studied with scalar relativistic, gradient-corrected (PBE) and hybrid (PBE0) density functional theory. The metal–Cp centroid distances shorten from ThCp3 to NpCp3, but lengthen again from PuCp3 to CmCp3. Examination of the valence molecular orbital structures reveals that the highest-lying Cp π2,3-based orbitals transform as 1e + 2e + 1a1 + 1a2. Above these levels come the predominantly metal-based 5f orbitals, which stabilise across the Actinide Series such that in CmCp3 the 5f manifold is at more negative energy than the Cp π2,3-based levels. Mulliken population analysis shows metal d orbital participation in the e symmetry Cp π2,3-based orbitals. Metal 5f character is found in the 1a1 and 1a2 levels, and this contribution increases significantly from ThCp3 to AmCp3. This is in agreement with the metal spin densities, which are enhanced above their formal value in NpCp3, PuCp3 and especially AmCp3 with both PBE and PBE0. However, atoms-in-molecules analysis of the electron densities indicates that the An–Cp bonding is very ionic, increasingly so as the Actinide becomes heavier. It is concluded that the large metal orbital contributions to the Cp π2,3-based levels, and enhanced metal spin densities toward the middle of the Actinide Series arise from a coincidental energy match of metal and ligand orbitals, and do not reflect genuinely increased covalency (in the sense of appreciable overlap between metal and ligand levels and a build up of electron density in the region between the Actinide and carbon nuclei).

Brian L. Scott - One of the best experts on this subject based on the ideXlab platform.

Florent Réal - One of the best experts on this subject based on the ideXlab platform.

  • Properties of the tetravalent Actinide Series in aqueous phase from a microscopic simulation self-consistent engine.
    Physical chemistry chemical physics : PCCP, 2020
    Co-Authors: Eléonor Acher, Michel Masella, Valérie Vallet, Florent Réal
    Abstract:

    In the context of nuclear fuel recycling and environmental issues, the understanding of the properties of radio-elements with various approaches remains a challenge regarding their dangerousness. Moreover, experimentally, some issues are also of importance; first, it is imperative to work at sufficiently high concentrations to reach the sensitivities of the analytical tools, however this condition often leads to precipitation for some of them; second, stabilizing specific oxidation states of some Actinides remains a challenge, thus making it difficult to extract general trends across the Actinide Series. Complementary to experiments, modeling can be used to unbiasedly probe the Actinide's properties in an aquatic environment and offers a predictive tool. We report the first molecular dynamics simulations based on homogeneously built force fields for the whole Series of the tetravalent Actinides in aqueous phase from ThIV to BkIV and including PuIV. The force fields used to model the interactions among the constituents include polarization and charge donation microscopic effects. They are built from a self-consistent iterative ab initio based engine that can be included in future developments as an element of a potential machine learning procedure devoted to generating accurate force fields. The comparison of our simulated hydrated Actinide properties to available experimental data shows the model robustness and the relevance of our parameter assignment engine. Moreover, our simulated structural, dynamical and evolution of the hydration free energy data show that, apart from AmIV and CmIV, the Actinide properties change progressively along the Series.

  • Properties of the tetravalent Actinide Series in aqueous phase from a microscopic simulation automated engine
    Physical Chemistry Chemical Physics, 2020
    Co-Authors: Eléonor Acher, Michel Masella, Valérie Vallet, Florent Réal
    Abstract:

    In the context of nuclear fuel recycling and environmental issues, the understanding of the properties of radio-elements with various approaches remains a challenge regarding their dangerous- ness. Moreover, experimentally, it is imperative to work at sufficiently high concentrations to reach the sensitivities of the analysis tools, which often leads to precipitation for some of them, and sta- bilizing of specific oxidation states of some Actinides remains a challenge, thus making it difficult to extract general trends across the Actinide Series. Complementary to experiments, modelling can be used to unbiasedly probe the Actinide’s properties in aquatic environment and offers a predictive tool. We report the first molecular dynamics simulations based on homogeneously built force fields for the whole Series of the tetravalent Actinides in aqueous phase from ThIV to BkIV and including PuIV. The force fields used to model the interactions among the constituents include polarization and charge donation microscopic effects. They are built from an automated iterative ab initio based engine, the core element of a future machine learning procedure devoted to generate accurate force fields. The comparison of our simulated hydrated Actinide properties to available experimental data show the model robustness and the relevance of our parameter assignment engine. Moreover our simulated structural, dynamical and hydration free energy data show that, apart from AmIV and CmIV, the Actinides properties change progressively along the Series.

  • properties of the tetravalent Actinide Series in aqueous phase from a microscopic simulation automated engine
    arXiv: Chemical Physics, 2019
    Co-Authors: Eléonor Acher, Michel Masella, Valérie Vallet, Florent Réal
    Abstract:

    In the context of nuclear fuel recycling and environmental issues, the understanding of the properties of radio-elements with various approaches remains a challenge regarding their dangerousness. Moreover, experimentally, it is imperative to work at sufficiently high concentrations to reach the sensitivities of the analysis tools, which often leads to precipitation for some of them, and stabilizing of specific oxidation states of some Actinides remains a challenge, thus making it difficult to extract general trends across the Actinide Series. Complementary to experiments, modelling can be used to unbiasedly probe the Actinide's properties in aquatic environment and offers a predictive tool. We report the first molecular dynamics simulations based on homogeneously built force fields for the whole Series of the tetravalent Actinides in aqueous phase from $\mathrm{Th^{IV}}$ to $\mathrm{Bk^{IV}}$ and including $\mathrm{Pu^{IV}}$. The force fields used to model the interactions among the constituents include polarization and charge donation microscopic effects. They are built from an automated iterative \textit{ab initio} based engine, the core element of a future machine learning procedure devoted to generate accurate force fields. The comparison of our simulated hydrated Actinide properties to available experimental data show the model robustness and the relevance of our parameter assignment engine. Moreover our simulated structural, dynamical and hydration free energy data show that, apart from $\mathrm{Am^{IV}}$ and $\mathrm{Cm^{IV}}$, the Actinides properties change progressively along the Series.

Evelyne Brichet - One of the best experts on this subject based on the ideXlab platform.

  • Actinide Series disequilibrium as a tool to establish the chronology of deep sea hydrothermal activity
    Geochimica et Cosmochimica Acta, 1993
    Co-Authors: Claude Lalou, Jean Louis Reyss, Evelyne Brichet
    Abstract:

    This paper describes the different radiochronological methods used to date geologically recent (i.e., <400,000 years) deep-sea hydrothermal deposits as well as the basic conditions necessary to obtain reliable dates. The limitations of the different techniques also are described. Using measurements of 210PbPb, 228Th228Ra, 230Th234U, 231Pa235U and 228Ra226Ra, the authors have undertaken an exhaustive chronological study of the hydrothermal deposits along the East Pacific Rise, the Mid-Atlantic Ridge, and in some back-arc basins. The objectives of this study were to obtain regional chronologies and to establish a general synthesis on the evolution of the hydrothermal processes at the scale of the mid-oceanic ridge system. Some results obtained by other authors are included in this synthesis. The dependence of the general trends of temporal development of the hydrothermal chimneys, edifices, and fields on their tectonic settings is discussed. This study demonstrates that hydrothermal activity does not represent a regular input of matter to the ocean, and that its pulsed character must be taken into account in all modeling attempts (chemical, biological and tectonic) affected by hydrothermal processes. In areas of rapid spreading, like the East Pacific Rise, recent and fossil deposits are spatially separated. By contrast, at the slow spreading Mid-Atlantic Ridge, fossil and present activity are found in the same location.

  • Actinide-Series disequilibrium as a tool to establish the chronology of deep-sea hydrothermal activity☆
    Geochimica et Cosmochimica Acta, 1993
    Co-Authors: Claude Lalou, Jean Louis Reyss, Evelyne Brichet
    Abstract:

    This paper describes the different radiochronological methods used to date geologically recent (i.e.,