Browsing by Author "Giansiracusa, MJ"

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    Ab initio calculations as a quantitative tool in the inelastic neutron scattering study of a single-molecule magnet analogue
    (Royal Society of Chemistry (RSC), 2016-02-04) Vonci, M; Giansiracusa, MJ; Gable, RW; Van den Heuvel, W; Latham, K; Moubaraki, B; Murray, KS; Yu, DH; Mole, RA; Soncini, A; Boskovic, C
    Ab initio calculations carried out on the Tb analogue of the single-molecule magnet family Na9[Ln(W5O18)2] (Ln = Nd, Gd, Ho and Er) have allowed interpretation of the inelastic neutron scattering spectra. The combined experimental and theoretical approach sheds new light on the sensitivity of the electronic structure of the Tb(III) ground and excited states to small structural distortions from axial symmetry, thus revealing the subtle relationship between molecular geometry and magnetic properties of the two isostructural species that comprise the sample. © The Royal Society of Chemistry 2016.
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    Inelastic neutron scattering of lanthanoid single molecule magnets
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Vonci, M; Giansiracusa, MJ; Mole, RA; Soncini, A; Boskovic, C
    With their signature energy barrier to magnetic relaxation and quantum tunnelling through this barrier, single-molecule magnets (SMMs) are important candidate molecules for future applications in molecular spintronics and quantum computation. Among the most promising SMMs are those based on trivalent lanthanoid ions (Ln-SMMs). One of the most powerful experimental techniques for elucidating the electronic structure of SMMs is inelastic neutron scattering (INS), which provides a direct probe of the relevant energy levels. INS is very sensitive to the electronic structure of the lowest lying energy levels of Ln(III) ions, which are dominated by crystal field (CF) splitting effects. Despite these advantages, relatively few INS spectra with well-defined magnetic scattering have been reported for Ln-SMMs. We have recently completed a study of two structural families of Ln(III)-polyoxometalates: Na9[Ln(W5O18)2] (Ln = Nd, Tb, Ho, Er) and Na11[{Ln(OH2)}3CO3(PW9O34)2], (Ln = Ho, Er). In both cases the INS measurements have been analysed using both a conventional crystal field and a more comprehensive ab initio approach. In the current contribution I will address the issues related to getting high quality neutron scattering data and summarise what has been learnt about the rational design of SMMs from this series of experiments.
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    Magnetic excitations in polyoxotungstate-supported lanthanoid single-molecule magnets: an inelastic neutron scattering and ab initio study
    (American Chemical Society, 2016-01-03) Vonci, M; Giansiracusa, MJ; Van den Heuvel, W; Gable, RW; Moubaraki, B; Murray, KS; Yu, DH; Mole, RA; Soncini, A; Boskovic, C
    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: Na9[Ln(W5O18)2] (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 LnIII ground multiplets and the experimentally measured magnetic and spectroscopic properties for the various analogs of the Na9[Ln(W5O18)2] family. © 2016 American Chemical Society.