Theoretical Framework for Modeling Field-Dependent Properties of Molecule-Based Magnetic Materials by using Spin-Flips
Final Report Abstract
In this research project, I developed high-accuracy computer models that facilitate the design of new magnetic materials, specifically single-molecule magnets (SMMs). In SMMs, unpaired electrons align their magnetic moments (their spins) to form a magnet. A major advantage of SMM magnetic units is that they can consist of much fewer atoms than regular magnetic materials. Thus, they require less space. This will facilitate their application in novel data storage materials with up to 10000x higher information density compared to current materials. Also, SMMs can exhibit quantum behavior, allowing their use as qubits, the building blocks of quantum computers. SMMs rely on precise control over the interactions between spins that still require improvement to become application-ready: SMMs suffer from unwanted interactions so that their magnetization only remains stable for short times and at very low temperatures. Researchers use theoretical models called spin Hamiltonians to guide the development of improved magnetic materials. In quantum chemical calculations on systems with unpaired electrons, it is challenging to consider the many different electron configurations that occur. During this project, I tested multiple methods for calculating spin Hamiltonian parameters that use one single electron configuration and generate all other required configurations by adding or removing electrons. Compared to previous theoretical studies, my results reach similar or improved agreement with experimental results. Since single reference methods require less computing time for larger systems than the previously available theoretical methods, future studies can use this approach to predict properties of candidate SMM systems before they are synthesized but also identify design principles that maximize the stability of the magnetic polarization.
Publications
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Python code to calculate spin Hamiltonians from local orbital, part of “ezMagnets” Python library
Alessio M. & Krylov A.
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Software for the frontiers of quantum chemistry: An overview of developments in the Q-Chem 5 package. The Journal of Chemical Physics, 155(8).
Epifanovsky, Evgeny; Gilbert, Andrew T. B.; Feng, Xintian; Lee, Joonho; Mao, Yuezhi; Mardirossian, Narbe; Pokhilko, Pavel; White, Alec F.; Coons, Marc P.; Dempwolff, Adrian L.; Gan, Zhengting; Hait, Diptarka; Horn, Paul R.; Jacobson, Leif D.; Kaliman, Ilya; Kussmann, Jörg; Lange, Adrian W.; Lao, Ka Un; Levine, Daniel S. ... & Krylov, Anna I.
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Magnetic exchange interactions in binuclear and tetranuclear iron(III) complexes described by spin‐flip DFT and Heisenberg effective Hamiltonians. Journal of Computational Chemistry, 44(3), 367-380.
Kotaru, Saikiran; Kähler, Sven; Alessio, Maristella & Krylov, Anna I.
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State-Interaction Approach for Evaluating g-Tensors within EOM-CC and RAS-CI Frameworks: Theory and Benchmarks. The Journal of Physical Chemistry A, 127(40), 8459-8472.
Kähler, Sven; Cebreiro-Gallardo, Antonio; Pokhilko, Pavel; Casanova, David & Krylov, Anna I.
