Magnetic Energy Landscape of Dimolybdenum Tetraacetate on a Bulk Insulator Surface

Abstract

The magnetic states and the magnetic anisotropy barrier of a transition metal molecular complex, dimolybdenum tetraacetate, are investigated via density functional theory (DFT). Calculations are performed in the gas phase and on a calcite (10.4) bulk insulating surface, using the Generalized-Gradient Approximation (GGA)-PBE and the Hubbard-corrected DFT + U and DFT + U + V functionals. The molecular complex (denoted MoMo) contains two central metallic molybdenum atoms, embedded in a square cage of acetate groups. Recently, MoMo was observed to form locally regular networks of immobile molecules on calcite (10.4), at room conditions. As this is the first example of a metal-coordinated molecule strongly anchored to an insulator surface at room temperature, we explore here its magnetic properties with the aim to understand whether the system could be assigned features of a single molecule magnet (SMM) and could represent the basis to realize stable magnetic networks on insulators. After an introductory review on SMMs, we show that, while the uncorrected GGA-PBE functional stabilizes MoMo in a nonmagnetic state, the DFT + U and DFT + U + V approaches stabilize an antiferromagnetic ground state and several meta-stable ferromagnetic and ferrimagnetic states. Importantly, the energy landscape of magnetic states remains almost unaltered on the insulating surface. Finally, via a noncollinear magnetic formalism and a newly introduced algorithm, we calculate the magnetic anisotropy barrier, whose value indicates the stability of the molecule’s magnetic moment.

Importance of intersite Hubbard interactions in $β$-MnO$_2$: A first-principles DFT+$U$+$V$ study

“…Similar trends were found in Ref. [80] for molecular systems. This means that the sensitivity of U and V to the spin configuration of β-MnO 2 is not very strong but at the same time it is not negligible (especially in the OAO case).…”

“…in Refs. [80,[86][87][88]. Therefore, we adopt the same strategy and apply it in this work for β-MnO 2 .…”

Pivotal Role of Intersite Hubbard Interactions in Fe-Doped α-MnO2

“…Herein, we present a fully first-principles study of the structural, electronic, and magnetic properties of the pristine and Fe-doped α-MnO 2 using DFT with extended Hubbard functionals (DFT+ U + V ) . The DFT+ U + V approach has proven to be effective for accurate description of various properties of solids and molecules. ,− We compute the onsite U and intersite V Hubbard parameters using density-functional perturbation theory (DFPT) , in the basis of Löwdin-orthogonalized atomic orbitals. Thus, we avoid any empiricism and ambiguities that are so common to the vast majority of other DFT+ U studies.…”

Accurate electronic properties and intercalation voltages of olivine-type Li-ion cathode materials from extended Hubbard functionals

“…With this choice of projector functions the electrons in the intersite overlap regions are not counted twice when computing the atomic occupations used in the Hubbard correction, as it is instead the case for the nonorthogonalized atomic orbitals φ I m (r). As a matter of fact, DFT+Hubbard with the Löwdin orthogonalized orbitals have proven to give more accurate results for various properties of materials [67][68][69][70][71][72], provided the Hubbard parameters are consistently computed with the Löwdin orthogonalized orbitals. Therefore, Hubbard parameters and Hubbard projectors should always be defined consistently and reported together.…”