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Computational Modelling of Magnetic Molecules and Multifunctional Magnetic Materials

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A special issue of Magnetochemistry (ISSN 2312-7481). This special issue belongs to the section "Magnetic Materials".

Deadline for manuscript submissions: closed (20 December 2021) | Viewed by 16445

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Special Issue Editor

Dr. Alessandro Lunghi

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Guest Editor

School of Physics, Trinity College Dublin, Dublin 2, Ireland
Interests: molecular magnetism; spin quantum technologies; spin relaxation; spin–phonon interaction; theoretical chemistry; computational chemistry; machine learning

Special Issue Information

Dear Colleagues,

The field of computational modelling of magnetic materials is witnessing exciting times. Now more than ever, with the increasing efficiency and accuracy of ab initio simulations and the advent of machine learning methods, computational sciences are at the forefront of scientific innovation.

Quantum chemistry has played a fundamental role in the advances in molecular magnetism and it remains a fundamental force driving the design of new magnetic materials. However, many different computational disciplines are now needed to provide a comprehensive understanding of complex and dynamic magnetic phenomena. Theory and modelling of spin relaxation, spin transport, and molecular dynamics are only a few of the many fields of growing interest for the communities working on magnetic materials and spin-based quantum technologies.

This special issue of Magnetochemistry aims to provide an overview of the many branches of the state-of-the-art advances in this rapidly evolving field and it aspires to showcase the most important advances in the computational modelling of magnetic molecules and multifunctional magnetic materials.

Dr. Alessandro Lunghi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Magnetochemistry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

ab initio simulations
data-driven methods
machine learning
magnetic materials
molecular magnets
molecular qubits
spin relaxation
molecular anisotropy
molecular spintronics
spin crossover
metal–organic frameworks
multifunctional materials

Published Papers (5 papers)

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Research

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15 pages, 2051 KiB

Open AccessArticle

The Role of Magnetic Dipole—Dipole Coupling in Quantum Single-Molecule Toroics

by Kieran Hymas and Alessandro Soncini

Magnetochemistry 2022, 8(5), 58; https://doi.org/10.3390/magnetochemistry8050058 - 23 May 2022

Cited by 4 | Viewed by 2995

Abstract

For single-molecule toroics (SMTs) based on noncollinear Ising spins, intramolecular magnetic dipole–dipole coupling favours a head-to-tail vortex arrangement of the semi-classical magnetic moments associated with a toroidal ground state. However, to what extent does this effect survive beyond the semi-classical Ising limit? Here, we theoretically investigate the role of dipolar interactions in stabilising ground-state toroidal moments in quantum Heisenberg rings with and without on-site magnetic anisotropy. For the prototypical triangular SMT with strong on-site magnetic anisotropy, we illustrate that, together with noncollinear exchange, intramolecular magnetic dipole–dipole coupling serves to preserve ground-state toroidicity. In addition, we investigate the effect on quantum tunnelling of the toroidal moment in Kramers and non-Kramers systems. In the weak anisotropy limit, we find that, within some critical ion–ion distances, intramolecular magnetic dipole–dipole interactions, diagonalised over the entire Hilbert space of the quantum system, recover ground-state toroidicity in ferromagnetic and antiferromagnetic odd-membered rings with up to seven sites, and are further stabilised by Dzyaloshinskii–Moriya coupling. Full article

(This article belongs to the Special Issue Computational Modelling of Magnetic Molecules and Multifunctional Magnetic Materials)

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10 pages, 2446 KiB

Open AccessArticle

Predicting Pt-195 NMR Chemical Shift and ¹J(¹⁹⁵Pt-³¹P) Coupling Constant for Pt(0) Complexes Using the NMR-DKH Basis Sets

by Joyce H. C. e Silva, Hélio F. Dos Santos and Diego F. S. Paschoal

Magnetochemistry 2021, 7(11), 148; https://doi.org/10.3390/magnetochemistry7110148 - 12 Nov 2021

Cited by 4 | Viewed by 2483

Abstract

Pt(0) complexes have been widely used as catalysts for important reactions, such as the hydrosilylation of olefins. In this context, nuclear magnetic resonance (NMR) spectroscopy plays an important role in characterising of new structures and elucidating reaction mechanisms. In particular, the Pt-195 NMR is fundamental, as it is very sensitive to the ligand type and the oxidation state of the metal. In the present study, quantum mechanics computational schemes are proposed for the theoretical prediction of the Pt-195 NMR chemical shift and ¹J(¹⁹⁵Pt–³¹P) in Pt(0) complexes. The protocols were constructed using the B3LYP/LANL2DZ/def2-SVP/IEF-PCM(UFF) level for geometry optimization and the GIAO-PBE/NMR-DKH/IEF-PCM(UFF) level for NMR calculation. The NMR fundamental quantities were then scaled by empirical procedures using linear correlations. For a set of 30 Pt(0) complexes, the results showed a mean absolute deviation (MAD) and mean relative deviation (MRD) of only 107 ppm and 2.3%, respectively, for the Pt-195 NMR chemical shift. When the coupling constant is taken into account, the MAD and MRD for a set of 33 coupling constants in 26 Pt(0) complexes were of 127 Hz and 3.3%, respectively. In addition, the models were validated for a group of 17 Pt(0) complexes not included in the original group that had MAD/MRD of 92 ppm/1.7% for the Pt-195 NMR chemical shift and 146 Hz/3.6% for the ¹J(¹⁹⁵Pt–³¹P). Full article

(This article belongs to the Special Issue Computational Modelling of Magnetic Molecules and Multifunctional Magnetic Materials)

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19 pages, 1639 KiB

Open AccessFeature PaperArticle

Simulating Static and Dynamic Properties of Magnetic Molecules with Prototype Quantum Computers

by Luca Crippa, Francesco Tacchino, Mario Chizzini, Antonello Aita, Michele Grossi, Alessandro Chiesa, Paolo Santini, Ivano Tavernelli and Stefano Carretta

Magnetochemistry 2021, 7(8), 117; https://doi.org/10.3390/magnetochemistry7080117 - 12 Aug 2021

Cited by 15 | Viewed by 3004

Abstract

Magnetic molecules are prototypical systems to investigate peculiar quantum mechanical phenomena. As such, simulating their static and dynamical behavior is intrinsically difficult for a classical computer, due to the exponential increase of required resources with the system size. Quantum computers solve this issue by providing an inherently quantum platform, suited to describe these magnetic systems. Here, we show that both the ground state properties and the spin dynamics of magnetic molecules can be simulated on prototype quantum computers, based on superconducting qubits. In particular, we study small-size anti-ferromagnetic spin chains and rings, which are ideal test-beds for these pioneering devices. We use the variational quantum eigensolver algorithm to determine the ground state wave-function with targeted ansatzes fulfilling the spin symmetries of the investigated models. The coherent spin dynamics are simulated by computing dynamical correlation functions, an essential ingredient to extract many experimentally accessible properties, such as the inelastic neutron cross-section. Full article

(This article belongs to the Special Issue Computational Modelling of Magnetic Molecules and Multifunctional Magnetic Materials)

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Review

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30 pages, 957 KiB

Open AccessReview

The Microscopic Mechanisms Involved in Superexchange

by Jacques Curély

Magnetochemistry 2022, 8(1), 6; https://doi.org/10.3390/magnetochemistry8010006 - 30 Dec 2021

Cited by 3 | Viewed by 2071

Abstract

In earlier work, we previously established a formalism that allows to express the exchange energy J vs. fundamental molecular integrals without crystal field, for a fragment A–X–B, where A and B are 3d¹ ions and X is a closed-shell diamagnetic ligand. In this article, we recall this formalism and give a physical interpretation: we may rigorously predict the ferromagnetic (J < 0) or antiferromagnetic (J > 0) character of the isotropic (Heisenberg) spin-spin exchange coupling. We generalize our results to nd^m ions (3 ≤ n ≤ 5, 1 ≤ m ≤ 10). By introducing a crystal field we show that, starting from an isotropic (Heisenberg) exchange coupling when there is no crystal field, the appearance of a crystal field induces an anisotropy of exchange coupling, thus leading to a z-z (Ising-like) coupling or a x-y one. Finally, we discuss the effects of a weak crystal field magnitude (3d ions) compared to a stronger (4d ions) and even stronger one (5d ions). In the last step, we are then able to write the corresponding Hamiltonian exchange as a spin-spin one. Full article

(This article belongs to the Special Issue Computational Modelling of Magnetic Molecules and Multifunctional Magnetic Materials)

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18 pages, 8102 KiB

Open AccessReview

Methods and Models of Theoretical Calculation for Single-Molecule Magnets

by Qian-Cheng Luo and Yan-Zhen Zheng

Magnetochemistry 2021, 7(8), 107; https://doi.org/10.3390/magnetochemistry7080107 - 28 Jul 2021

Cited by 14 | Viewed by 4677

Abstract

Theoretical calculation plays an important role in the emerging field of single-molecule magnets (SMMs). It can not only explain experimental phenomena but also provide synthetic guidance. This review focuses on discussing the computational methods that have been used in this field in recent years. The most common and effective method is the complete active space self-consistent field (CASSCF) approach, which predicts mononuclear SMM property very well. For bi- and multi-nuclear SMMs, magnetic exchange needs to be considered, and the exchange coupling constants can be obtained by Monte Carlo (MC) simulation, ab initio calculation via the POLY_ANISO program and density functional theory combined with a broken-symmetry (DFT-BS) approach. Further application for these calculation methods to design high performance SMMs is also discussed. Full article

(This article belongs to the Special Issue Computational Modelling of Magnetic Molecules and Multifunctional Magnetic Materials)

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