A quantum chemical study of endometallofullerenes: Gd@C 70 , Gd@C 82 , Gd@C 84 , and Gd@C 90
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THE EUROPEAN PHYSICAL JOURNAL D
Regular Article
A quantum chemical study of endometallofullerenes: Gd@C70, Gd@C82, Gd@C84, and Gd@C90 Anna V. Zakharova1,2,a and Marina E. Bedrina1 1 2
St. Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia Petersburg Nuclear Physics Institute Named by B.P. Konstantinov of National Research Centre “Kurchatov Institute”, mkr. Orlova roshcha 1, Gatchina 188300, Russia Received 24 February 2020 / Received in final form 16 April 2020 Published online 16 June 2020 c EDP Sciences / Societ`
a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2020 Abstract. Quantum chemical (U)PBE0 method is used to investigate the endometallofullerenes Gd@C70 , Gd@C82 , Gd@C84 , and Gd@C90 for different spin states. The equilibrium structural parameters, IR spectra, the chemical bond energies, the electron affinity and vertical ionization potentials are calculated. The analysis of the electron and spin populations of the atomic orbitals in gadolinium endocomplexes was carried out. For all considered configurations, the calculations predict the polarizability depression and a high value of the magnetic moment. The endocomplex has the same high value of multi-electron spin as the free gadolinium atom, that characterizes its significant magnetic properties.
1 Introduction Integration of the metal atoms into the carbon cage of fullerene allows forming new structures – endometallofullerenes. The transfer of electrons from the endoatom to the carbon cage changes the energy and electrochemical properties of the system. The determination of the metal atom position inside the carbon cage is necessary for determination of the new material properties. For the synthesis of rare-earth endohedral fullerenes, various methods are used, in particular, for Ln@C2n (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb), the method of high-temperature pyridine extraction under high pressure has been successfully used [1]. Rareearth endometallofullerenes are investigated by electron paramagnetic resonance (EPR spectroscopy). The EPR spectra for Gd@C82 powder and solution (T = 4–20 K) were measured in [2]. The magnetic properties of some heavy rare-earth metallofullerenes were studied by various methods [3–5]. It was found that the decrease in magnetic moment and the “wrong” paramagnetic behavior of M@C82 (M = Gd, Tb, Dy, Ho, and Er) are related to the orbital angular momentum of the trapped M3+ ions [5]. In the paper [6] the Gd@C82 magnetic moment was obtained theoretically. The calculations are based on the Hartree–Fock approximation with relativistic corrections. It was obtained that the ground and excited electronic configurations of Gd in a trivalent state are 3d10 4f 7 and 3d9 4f 8 . The trivalence of Gd atoms in the metallofullerene Gd@C82 is also supported by electron energy-loss spectroscopy experiment [7]. a
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Early investigations in this field have shown the formation of some gadolinium endocomplexes with a number of
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