showing 10 related works from this author
Ab initio calculations of the transfer parameters and coulombic repulsion and estimation of their effects on the electron delocalization and magnetic…
2003
International audience; In this work, we present ab initio calculations on embedded fragments that permit to extract the value of the effective electron transfer integral and coulombic repulsion between W nearest neighbour atoms in a mixed-valence αPW12O40 Keggin polyoxoanion. This allows us to perform a quantitative study of the influence of these two parameters on the magnetic properties of Keggin polyoxoanions reduced by two electrons. We surprisingly find that the electron transfer between edge-sharing and corner-sharing WO6 octahedra have very close values, and show that the punctual charges estimation of coulombic repulsion may not be accurate enough to study the electronic distributi…
Electron Delocalization and Electrostatic Repulsion at the Origin of the Strong Spin Coupling in Mixed-Valence Keggin Polyoxometalates: Ab Initio Cal…
2004
International audience; Cet article détaille une procédure générale qui associe l′évaluation de paramètres microscopiques et la prédiction de propriétés macroscopiques. Les principales interactions entre les électrons délocalisés sur des polyoxométalates à valence mixte sont extraites à partir du calcul de la spectroscopie de valence de fragments immergés dans un bain qui reproduit les principaux effets du reste du cristal sur le fragment considéré. Nous avons extrait non seulement la valeur du transfert électronique, du couplage magnétique et du paramètre de "exchange-transfer" entre ions métalliques premiers et seconds voisins, mais encore la valeur de la répulsion électrostatique entre l…
Modelling electric field control of the spin state in the mixed-valence polyoxometalate [GeV14O40]8−
2013
International audience; : The two-electron reduced mixed-valence polyoxometalate [GeV14O40](8-) presents an unusual paramagnetic behaviour as a consequence of the partial trapping of these electrons. The effect of applying an electric field is that of inducing antiferromagnetic coupling between the two delocalized electronic spins.
Origin of the Paramagnetic Properties of the Mixed‐Valence Polyoxometalate [GeV 14 O 40 ] 8– Reduced by Two Electrons: Wave Function Theory and Model…
2009
The aim of the work is to give an explanation of the magnetic properties of a mixed-valence [GeV14O40]8– polyoxometalate reduced by two electrons, which, in contrast to what happens in other two-electron-reduced polyoxometalates, does not show any magnetic coupling between the two unpaired electrons. For this purpose, a quantitative evaluation of the microscopic electronic parameters (electron transfer, magnetic coupling, magnetic orbital energy, and Coulomb repulsion) of the mixed-valence polyoxometalate cluster is performed. The parameters are extracted from valence-spectroscopy large configuration interaction (CI) calculations on embedded fragments. Then, these parameters are used in an …
Role of the electron transfer and magnetic exchange interactions in the magnetic properties of mixed-valence polyoxovanadate complexes.
2008
International audience; Modeling the properties of high-nuclearity, high-electron-population, mixed-valence (MV) magnetic systems remains one of the open challenges in molecular magnetism. In this work, we analyze the magnetic properties of a series of polyoxovananadate clusters of formula [V 18O 42] (12-) and [V 18O 42] (4-). The first compound is a fully localized spin cluster that contains 18 unpaired electrons located at the metal sites, while the second one is a MV cluster with 10 unpaired electrons largely delocalized over the 18 metal sites. A theoretical model that takes into account the interplay between electron transfer and magnetic exchange interactions is developed to explain t…
Electron delocalization in mixed-valence Keggin polyoxometalates. Ab initio calculation of the local effective transfer integrals and its consequence…
2002
We present a quantitative evaluation of the influence of the electron transfer on the magnetic properties of mixed-valence polyoxometalates reduced by two electrons. For that purpose, we extract from valence-spectroscopy ab initio calculations on embedded fragments the value of the transfer integrals between W nearest-neighbor atoms in a mixed-valence alphaPW(12)O(40) polyoxowolframate Keggin anion. In contradiction with what is usually assumed, we show that the electron transfer between edge-sharing and corner-sharing WO(6) octahedra have very close values. Considering fragments of various ranges, we analyze the accuracy of calculations on fragments based on only two WO(5) pyramids which s…
Quantum Cellular Automata: a Short Overview of Molecular Problem
2018
International audience
Electrically switchable magnetic molecules: inducing a magnetic coupling by means of an external electric field in a mixed-valence polyoxovanadate cl…
2015
International audience; Herein we evaluate the influence of an electric field on the coupling of two delocalized electrons in the mixed-valence polyoxometalate (POM) [GeV14 O40 ](8-) (in short V14 ) by using both a t-J model Hamiltonian and DFT calculations. In absence of an electric field the compound is paramagnetic, because the two electrons are localized on different parts of the POM. When an electric field is applied, an abrupt change of the magnetic coupling between the two delocalized electrons can be induced. Indeed, the field forces the two electrons to localize on nearest-neighbors metal centers, leading to a very strong antiferromagnetic coupling. Both theoretical approaches have…
A Wigner molecule at extremely low densities: a numerically exact study
2019
In this work we investigate Wigner localization at very low densities by means of the exact diagonalization of the Hamiltonian. This yields numerically exact results. In particular, we study a quasi-one-dimensional system of two electrons that are confined to a ring by three-dimensional gaussians placed along the ring perimeter. To characterize the Wigner localization we study several appropriate observables, namely the two-body reduced density matrix, the localization tensor and the particle-hole entropy. We show that the localization tensor is the most promising quantity to study Wigner localization since it accurately captures the transition from the delocalized to the localized state an…
Determining Key Local Vibrations in the Relaxation of Molecular Spin Qubits and Single-Molecule Magnets.
2017
To design molecular spin qubits and nanomagnets operating at high temperatures, there is an urgent need to understand the relationship between vibrations and spin relaxation processes. Herein we develop a simple first-principles methodology to determine the modulation that vibrations exert on spin energy levels. This methodology is applied to [Cu(mnt)2]2– (mnt2– = 1,2-dicyanoethylene-1,2-dithiolate), a highly coherent complex. By theoretically identifying the most relevant vibrational modes, we are able to offer general strategies to chemically design more resilient magnetic molecules, where the energy of the spin states is not coupled to vibrations.