Papers by Alessandro Soncini
Chemical science, 2024
Magnetic exchange coupling can modulate the slow magnetic relaxation in single-molecule magnets. ... more Magnetic exchange coupling can modulate the slow magnetic relaxation in single-molecule magnets. Despite this, elucidation of exchange coupling remains a significant challenge for the lanthanoid(III) ions, both experimentally and computationally. In this work, the crystal field splitting and 4f-p exchange coupling in the erbium-semiquinonate complex [ErTp 2 dbsq] (Er-dbsq; Tp − = hydro-tris(1-pyrazolyl) borate, dbsqH 2 = 3,5-di-tert-butyl-1,2-semiquinone) have been determined by inelastic neutron scattering (INS), magnetometry, and CASSCF-SO ab initio calculations. A related complex with a diamagnetic ligand, [ErTp 2 trop] (Er-trop; tropH = tropolone), has been used as a model for the crystal field splitting in the absence of coupling. Magnetic and INS data indicate antiferromagnetic exchange for Er-dbsq with a coupling constant of J ex = −0.23 meV (−1.8 cm −1) (−2J ex formalism) and good agreement is found between theory and experiment, with the low energy magnetic and spectroscopic properties well modelled. Most notable is the ability of the ab initio modelling to reproduce the signature of interference between localised 4f states and delocalised p-radical states that is evident in the Qdependence of the exchange excitation. This work highlights the power of combining INS with EPR and magnetometry for determination of ground state properties, as well as the enhanced capability of CASSCF-SO ab initio calculations and purposely developed ab initio-based theoretical models. We deliver an unprecedentedly detailed representation of the entangled character of 4f-p exchange states, which is obtained via an accurate image of the spin-orbital transition density between the 4f-p exchange coupled wavefunctions.
Journal of Computational Chemistry, Nov 20, 2017
This is the author manuscript accepted for publication and has undergone full peer review but has... more This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version record. Please cite this article as
Inorganic Chemistry, Aug 23, 2022
Physical review, Jul 31, 2020
We present a theoretical study exposing the dominant microscopic electronic transport mechanisms ... more We present a theoretical study exposing the dominant microscopic electronic transport mechanisms underlying a recent molecular spin-transistor experiment [C. Godfrin et al., ACS Nano 11, 3984 (2017)], where purely electrical readout of the spin of a Tb(III)-based single-molecule magnet was achieved. To identify the relevant spin-to-charge conversion mechanisms enabling opposite spin polarizations of the Tb(III) ion 4 f electrons to generate different magnetoconductance responses, we investigate both incoherent sequential tunneling charge transport, and coherent cotunneling corrections. Contrary to previous interpretations invoking the highly coherent Kondo transport regime, we find that all reported experimental observations, including the temperature and magnetic field dependence of the differential conductance, can be reproduced reasonably well within a sequential tunneling transport regime explicitly accounting for broadening of the device energy levels due to molecule-lead coupling.
Resumo: Este artigo aborda a certificação de um produto eletrônico para atmosfera explosiva usand... more Resumo: Este artigo aborda a certificação de um produto eletrônico para atmosfera explosiva usando o princípio de proteção por segurança intrínseca. Expõe a parte teórica que envolve a classificação de áreas, a formação de atmosferas explosivas de gás e vapor, e o princípio de funcionamento da segurança intrínseca. Também é especificado um produto portátil, alimentado por bateria que possui as funcionalidades de monitoramento de transponders RFID e envio das informações para um sistema de gerenciamento centralizado com a finalidade de controlar o fluxo de combustível de uma unidade abastecedora e prevenir furtos. O produto e suas características construtivas são discutidas juntamente com a exposição dos requisitos normativos. São abordados o processo de certificação em si, o envolvimento da certificadora e dos laboratórios de ensaios, bem como o processo de auditoria e da emissão e manutenção do certificado. De forma a exemplificar o processo, os cálculos da análise teórica são demonstrados para assegurar que os parâmetros projetados atendem aos requisitos normativos. Palavras-chave: Segurança intrínseca. Atmosfera explosiva. Produto eletrônico.
Chemical Science, 2023
Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
Inorganic Chemistry, Jan 11, 2023
Physical Chemistry Chemical Physics, 2022
We present a multiconfigurationalab initiomethodology based on non-orthogonal fragments, quantita... more We present a multiconfigurationalab initiomethodology based on non-orthogonal fragments, quantitatively exposing metal–ligand non-covalent interaction contributions to crystal field energy levels and magnetic properties in lanthanide complexes.
Physical review, Sep 29, 2020
We present a time-dependent microscopic model for Coulomb blockade transport through an experimen... more We present a time-dependent microscopic model for Coulomb blockade transport through an experimentally realized supramolecular spin-valve device driven by an oscillating magnetic field, in which the 4f-electron magnetic states of an array of TbPc 2 single-molecule magnets (SMMs) were observed to modulate a sequential tunneling current through an underlying substrate nanoconstriction. Our model elucidates the dynamical mechanism at the origin of the observed hysteresis loops of the magnetoconductance, a signature of the SMMmodulated spin-valve effect, in terms of a phonon-assisted multi-spin-reversal cascade relaxation process, which mediates the switching of the device between the two conductive all-parallel spin configurations of the SMM array. Moreover, our proposed model can explain the zero-bias giant magnetoresistive transport gap measured in this device, solely within the incoherent transport regime, consistently with the experimental observations, as opposed to previous interpretations invoking Fano-resonance conductance suppression within a coherent ballistic transport regime. Finally, according to the proposed Coulomb blockade scenario, the SMM-mediated giant magnetoresistance effect is predicted to increase with the number of SMMs aligned on the nanoconstriction surface, on account of the increased number of intermediate nonconducting spin-flip states intervening in the phonon-assisted multi-spin-reversal cascade relaxation process necessary to switch between the two conducting all-parallel SMM spin configurations.
Angewandte Chemie, May 2, 2002
Carbon ions were implanted into nickel films to facilitate growth of few-layered graphene. After ... more Carbon ions were implanted into nickel films to facilitate growth of few-layered graphene. After vacuum annealing at 950 °C, G and 2D peaks were seen in micro-Raman measurements of the nickel film. No D peak, which is associated with sp3 adsorbates and vacancies/defects in graphene, was observed.
Physical review, Jun 10, 2019
We theoretically investigate a single-molecule magnet (SMM) grafted to a quantum dot in contact w... more We theoretically investigate a single-molecule magnet (SMM) grafted to a quantum dot in contact with metallic leads and interacting with a resonant electromagnetic radiation. We explore both the explicit timedependent behavior and the steady-state current-voltage characteristics of the device when the source lead is ferromagnetic. At zero-bias voltage, a net current is pumped through the device with the source spin current being reversed and amplified in the drain lead; this effect also persists for nonzero bias. We explain this effect in terms of spin transitions in the nanomagnet induced by the resonant radiation followed by their subsequent relaxation via spin-asymmetric charge-transfer processes. We demonstrate that the same effects are recovered in the time-averaged current when the device interacts with pulsed resonant radiation. Moreover, within the pulsed irradiation regime, appropriate choices of pulse length and wait times are shown here to allow the detection of coherent Rabi oscillations of the SMM spin states, via time-averaged spin current measurements.
Chemistry: A European Journal, Sep 17, 2018
The combination of lanthanoid nitrates with 18-crown-6 (18c-6) and tetrahalocatecholate (X 4 Cat ... more The combination of lanthanoid nitrates with 18-crown-6 (18c-6) and tetrahalocatecholate (X 4 Cat 2-, X = Cl, Br) ligands has afforded two compound series [Ln(18-c-6)(X 4 Cat)(NO 3)]•MeCN (X = Cl, 1-Ln; X = Br, 2-Ln; Ln = La, Ce, Nd, Gd, Tb, Dy). The 18-c-6 ligands occupy equatorial positions of a distorted sphenocorona geometry, while the charged ligands occupy the axial positions. The analogues of both series with Ln = Ce, Nd, Tb and Dy exhibit out-ofphase ac magnetic susceptibility signals in the presence of an applied magnetic field, indicative of slow magnetization relaxation. When diluted into a diamagnetic La host to reduce dipolar interactions, the Dy analogue exhibits slow relaxation up to 20 K in the absence of an applied dc field. Concerted magnetic measurements, EPR spectroscopy and ab initio calculations have allowed elucidation of the mechanisms responsible for slow magnetic relaxation. A consistent approach has been applied to quantitatively model the relaxation data for different lanthanoid analogues, suggesting that the spin dynamics are governed by Raman processes at higher temperatures, transitioning to a dominant phonon bottleneck process as the temperature is decreased, with an observed T-6 rather than the usual T-2 dependence (T is temperature). This anomalous thermal dependence of the phonon bottleneck relaxation is consistent with anharmonic effects in the lattice dynamics, which was predicted by Van Vleck more than 70 years ago.
ChemInform, Jul 1, 2016
Carbonate-Bridged Lanthanoid Triangles: Single-Molecule Magnet Behavior, Inelastic Neutron Scatte... more Carbonate-Bridged Lanthanoid Triangles: Single-Molecule Magnet Behavior, Inelastic Neutron Scattering, and ab initio Studies.-Compounds (IV) are characterized by single crystal XRD, magnetic measurements, inelastic neutron scattering, and CASSCF ab initio calculations. (IVa-e)•42H 2O crystallize in the monoclinic space group P2 1/n with Z = 4. The isostructural polyanions in these materials are comprised of a triangular arrangement of trivalent Ln ions bridged by a 3-carbonate ligand and sandwiched between two trilacunary Keggin-type {PW 9O34} polyoxometalate ligands. The magnetic and electronic properties of these compounds are discussed. Using phase-transfer methods the compounds (Et4N)9Na2[{Ln(OH2)}3CO3(PW9O34)2] (Ln: Y, Er) are obtained from (IVa,e).-(GIANSIRACUSA, M.
Organic and Biomolecular Chemistry, 2004
Journal of Chemical Physics, Oct 21, 2008
A self-consistent field (SCF) London-orbital computational scheme to perform gauge-origin indepen... more A self-consistent field (SCF) London-orbital computational scheme to perform gauge-origin independent nonperturbative calculations for molecules in strong magnetic fields is presented. The crucial difference in the proposed approach with respect to common-origin finite-field SCF implementations consists in the evaluation of molecular integrals over the field-dependent molecular basis functions, which is tantamount to computing molecular integrals in a hybrid Gaussian and plane-wave basis set. The implementation of a McMurchie–Davidson scheme for the calculation of the molecular integrals over London orbitals is discussed, and preliminary applications of the newly developed code to the calculation of fourth-rank hypermagnetizabilities for a set of small molecules, benzene, and cyclobutadiene are presented. The nonperturbative approach is particularly useful for studying the highly nonlinear response of paramagnetic closed-shell systems such as boron monohydride, or the π-electron response of cyclobutadiene.
Physical Chemistry Chemical Physics, 2022
This study on spin-orbit coupling descriptions of magnetic excitations in lanthanide complexes co... more This study on spin-orbit coupling descriptions of magnetic excitations in lanthanide complexes compares the accuracy in crystal field energies and magnetic anisotropies calculated using different approximations to the Breit-Pauli spin-orbit Hamiltonian.
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Papers by Alessandro Soncini