Toward exact predictions of spin-phonon relaxation times: An ab initio implementation of open quantum systems theory

Lunghi, Alessandro

doi:10.1126/sciadv.abn7880

Cited by 48 publications

(101 citation statements)

References 60 publications

(134 reference statements)

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“…The modes with high spin-phonon coupling constants (ν 12 , ν 15 , ν 16 , ν 26 , ν 28 , ν 29 ) also involve more shift in the first coordination sphere, probably due to molecular rotations and delocalized intramolecular distortions (see animated GIF files in SI). 38 Except for these six modes, the impact of spin-phonon coupling on magnetic anisotropy is just nominal (Figure 4). Accordingly for rest of the inspected modes, the corresponding g z values have not been diminished extensively, as reflected by small deviation in the magnitude of second derivatives (g ′ z ) of g z (Table S10 in SI).…”

Section: Spin-phonon Relaxation For Complexmentioning

confidence: 98%

“…Moreover, in order to accomplish and design SMMs operating at higher temperatures, the spin relaxation phenomena via vibronic couplings needs to be deciphered explicitly. 37,38 Therefore, we have attempted to determine the bottleneck effects of spin-vibrational coupling, prominently engendering the spin relaxation, for complex 1 having strong axial magnetic anisotropy.…”

Section: Introductionmentioning

confidence: 99%

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Impact of Spin-Phonon Coupling on Magnetic Relaxation of a Co(II) Single-Molecule Magnet

Nain¹,

Kumar²,

Ali³

2022

Preprint

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Single-molecule magnets (SMMs) based on transition metals have appeared as enticing targets exploiting the magnetic anisotropy in 3d elements. Among transition elements, Co based SMMs are very prominent as they often exhibit a high spin-reversal barrier (Ueff ), owing to large unquenched orbital angular momentum. Employing the wave function-based multireference CASSCF/NEVPT2 calculations, herein we substantiate the zero-field splitting parameters of four mononuclear Co complexes and one of them has been realized as a prospective SMM. The mechanism of magnetic relaxation has been studied to underpin the molecular origin of the slow relaxation of magnetization. The combination of suppressed quantum tunnelling of magnetization (QTM) at the ground state and the high negative D value usually manifests SMM behavior at zero-applied magnetic field. However, mere fulfillment of these conditions ensure little about their SMM behavior, as spin-phonon couplings often play the role of spoilsports by lowering the spin-relaxations channels. A detailed study accounting all the 46 vibrational modes below the first-excited state for the prospective Co(II) complex reveals one of the vibrational modes, providing lower spin-relaxation pathway and hence, resulting an SMM with Ueff value of 239.30 cm−1.

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Section: Spin-phonon Relaxation For Complexmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Impact of Spin-Phonon Coupling on Magnetic Relaxation of a Co(II) Single-Molecule Magnet

Nain¹,

Kumar²,

Ali³

2022

Preprint

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“…The vibrational DOS is constructed from uncalibrated harmonic frequencies broadened by antilorentzian line shapes of a constant line width parameter FWHM = 10 cm –1 . Further details, including rate expression for the Orbach and Raman regimes, are given in Section S1. , …”

Section: Computational Detailsmentioning

confidence: 99%

“…39,48 Spin dynamics calculations were carried out using the TAU software, implementing a semiclassical approach used in previous work. 4,8,11,49 Transition rates between different states are obtained by integrating the spin-one-phonon and spin-twophonon rate expressions 50 over the phonon DOS, weighted by Bose−Einstein occupation factors. The spin-phonon matrix elements are evaluated in the equilibrium CFP eigenbasis using CFP derivatives in normal mode coordinates.…”

mentioning

confidence: 99%

Analytic Linear Vibronic Coupling Method for First-Principles Spin-Dynamics Calculations in Single-Molecule Magnets

Staab

Chilton

2022

J. Chem. Theory Comput.

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Accurate modeling of vibronically driven magnetic relaxation from ab initio calculations is of paramount importance to the design of next-generation single-molecule magnets (SMMs). Previous theoretical studies have been relying on numerical differentiation to obtain spin-phonon couplings in the form of derivatives of spin Hamiltonian parameters. In this work, we introduce a novel approach to obtain these derivatives fully analytically by combining the linear vibronic coupling (LVC) approach with analytic complete active space self-consistent field derivatives and nonadiabatic couplings computed at the equilibrium geometry with a single electronic structure calculation. We apply our analytic approach to the computation of Orbach and Raman relaxation rates for a bis-cyclobutadienyl Dy(III) sandwich complex in the frozen-solution phase, where the solution environment is modeled by electrostatic multipole expansions, and benchmark our findings against results obtained using conventional numerical derivatives and a fully electronic description of the whole system. We demonstrate that our LVC approach exhibits high accuracy over a wide range of coupling strengths and enables significant computational savings due to its analytic, “single-shot” nature. Evidently, this offers great potential for advancing the simulation of a wide range of vibronic coupling phenomena in magnetism and spectroscopy, ultimately aiding the design of high-performance SMMs. Considering different environmental representations, we find that a point charge model shows the best agreement with the reference calculation, including the full electronic environment, but note that the main source of discrepancies observed in the magnetic relaxation rates originates from the approximate equilibrium electronic structure computed using the electrostatic environment models rather than from the couplings.

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“…smaller spin orbit coupling, their relaxation times are longer. 63,65,66 The narrower linewidth also implies that the µw rotor events are more efficient when irradiating the narrow line radical. 36 In addition, for a given magnetic field, MAS frequency and e-e couplings, CE and dipolar-J rotor events are favored thanks to the presence of the narrow line radical.…”

Section: Mas-dnp Field Sweep Profiles and Exchange Distributionmentioning

confidence: 99%

PyrroTriPol: a Semi-rigid Trityl-Nitroxide for High Field Dynamic Nuclear Polarization

Halbritter

Harrabi

Paul

et al. 2022

Preprint

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Magic angle spinning (MAS) dynamic nuclear polarization (DNP) has significantly broadened the scope of solid-state NMR to study biomolecular systems and materials. In recent years, the advent of very high field DNP combined with fast MAS has brought new challenges in the design of polarizing agents (PA) used to enhance nuclear spin polarization. Here, we present a trityl-nitroxide PA family based on a piperazine linker, named PyrroTriPol, for both aqueous and organic solutions. These new radicals have similar properties to that of TEMTriPol-I and can be readily synthesized, and purified in large quantities thereby ensuring widespread application. The family relies on a rigid bridge connecting the trityl and the nitroxide offering a better control of the electron spin-spin interactions thus providing improved performance across a broad range of magnetic fields and MAS frequencies while requiring reduced microwave power compared to bis-nitroxides. We demonstrate the efficiency of the PyrroTriPol family under a magnetic field of 9.4, 14.1 and 18.8 T with respect to TEMTriPol-I. In particular, the superiority of PyrroTriPol was demonstrated on γ-Al2O3 nanoparticles which enabled the acquisition of a high signal-to-noise surface-selective 27Al multiple-quantum MAS experiment at 18.8 T and 40 kHz MAS frequency

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Toward exact predictions of spin-phonon relaxation times: An ab initio implementation of open quantum systems theory

Cited by 48 publications

References 60 publications

Impact of Spin-Phonon Coupling on Magnetic Relaxation of a Co(II) Single-Molecule Magnet

Impact of Spin-Phonon Coupling on Magnetic Relaxation of a Co(II) Single-Molecule Magnet

Analytic Linear Vibronic Coupling Method for First-Principles Spin-Dynamics Calculations in Single-Molecule Magnets

PyrroTriPol: a Semi-rigid Trityl-Nitroxide for High Field Dynamic Nuclear Polarization

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