Liquid-state paramagnetic relaxation from first principles

Rantaharju, Jyrki; Vaara, Juha

doi:10.1103/physreva.94.043413

Cited by 9 publications

(11 citation statements)

References 32 publications

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“…In particular, the molecular order and fast motion of the spin moiety, be it solvent, lipid, or some other spin probe, are accessible from atomistic detail available from MD simulations. 14 , 15 , 19 , 25 The slower processes are modeled with BD simulation, and they consist, in the example case, of reorientation by translational dynamics. In this, the translational motion is intertwined with interface undulations simulated with Fourier space surface dynamics.…”

Section: Discussionmentioning

confidence: 99%

Brownian Translational Dynamics on a Flexible Surface: Nuclear Spin Relaxation of Fluid Membrane Phases

2018

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A general model for nuclear magnetic resonance (NMR) relaxation studies of fluid bilayer systems is introduced, combining a mesoscopic Brownian dynamics description of the bilayer with atomistic molecular dynamics (MD) simulations. An example is given for dipalmitoylphosphatidylcholine in 2H2O solvent and compared with the experiment. Experimental agreement is within a factor of 2 in the water relaxation rates, based on a postulated model with fixed parameters, which are largely available from the MD simulation. Relaxation rates are particularly sensitive to the translational diffusion of water perturbed by the interface dynamics and structure. Simulation results suggest that a notable deviation in the relaxation rates may follow from the commonly used small-angle approximation of bilayer undulation. The method has the potential to overcome the temporal and spatial limitations in computing NMR relaxation with atomistic MD, as well as the shortcomings of continuum models enabling a consistent description of experiments performed on a solvent lipid and added spin probes. This work opens for possibilities to understand relaxation processes involving systems such as micelles, multilamellar vesicles, red blood cells, and so forth at biologically relevant timescales in great detail.

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Section: Discussionmentioning

confidence: 99%

Brownian Translational Dynamics on a Flexible Surface: Nuclear Spin Relaxation of Fluid Membrane Phases

2018

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“…We simulated the time evolution of the combined electron-spin-nuclear-spin density operator separately for each event . A superpropagator of the form [17,18] was constructed, where the Liouvillian superoperatorL j relates toĤ j through eˆL j τσ = e −ihĤ j τσ e ihĤ j τ .…”

Section: Spin Dynamicsmentioning

confidence: 99%

“…Present techniques allow detailed investigation of such processes by combining molecular dynamics (MD) simulations of the atomic trajectories, quantum-chemical (QC) calculations to extract the instantaneous parameters of the relevant spin HamiltonianĤ (t ), and spin dynamics (SD) simulations of the spin system, driven by the time series of H . This approach has been applied to the electron [17] and both nuclear and electron [18] spin relaxation in an aqueous solution of Ni 2+ ion. In the present paper, we introduce a multiscale simulation procedure for the microscopic processes of SEOP [7,11,19], a hyperpolarization method that is in widespread materials science and clinical use [20,21].…”

Section: Introductionmentioning

confidence: 99%

Polarization transfer in a spin-exchange optical-pumping experiment

2020

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Spin-exchange optical pumping (SEOP) enables hyperpolarization of magnetic noble gas nuclei and allows enormously enhanced signal in nuclear magnetic resonance studies in materials, biosciences, and medicine. We model the dynamics of the SEOP process taking place in a Rb-129 Xe gas mixture and shed light on how the different microscopic processes influence the macroscopic polarization transfer. For each Rb-Xe collision taking place in simulated molecular dynamics trajectory, we sample a time series of quantum-chemically preparametrized Hamiltonians. Combined electron and nuclear spin dynamics of each event is propagated by solving the corresponding Liouville-von Neumann equation. The rarely occurring, long-lived van der Waals molecules are seen to give the most significant contribution to polarization transfer under the simulated conditions (T = 300 K, p = 2.4 bar), in agreement with earlier findings. Besides the lifetime of the collision complex, the average and minimum Rb-Xe interatomic distances characterize the efficiency of the polarization transfer events. We obtain insight into magnetization transfer in both individual binary collisions and van der Waals complexes and demonstrate a stepwise buildup of 129 Xe spin polarization upon bond-length oscillations in the latter.

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“…Later a model was developed for electron spin relaxation 13 through studying the fluctuations of the transient ZFS, obtained from solving the Smoluchowski equation for diffusion. More recently, AIMD simulations and density functional theory (DFT) calculations have been performed on aqueous Ni(II) [14][15][16][17] to report on the dynamical characteristics of the ion in solution and its paramagnetic shielding parameters. Furthermore, the same group has also performed complete active space self-consistent field (CASSCF) based studies to report on the paramagnetic shielding parameters of Ni(II) and other magnetic centers 18 .…”

Section: Introductionmentioning

confidence: 99%

An ab initio CASSCF study of zero field splitting fluctuations in the octet ground state of aqueous [Gd(iii)(HPDO3A)(H2O)]

Khan

Pollet

Vuilleumier

et al. 2017

The Journal of Chemical Physics

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In this work, we present ab initio calculations of the zero-field splitting (ZFS) of a gadolinium complex [Gd(iii)(HPDO3A)(HO)] sampled from an ab initio molecular dynamics (AIMD) simulation. We perform both post-Hartree-Fock (complete active space self-consistent field-CASSCF) and density functional theory (DFT) calculations of the ZFS and compare and contrast the methods with experimental data. Two different density functional approximations (TPSS and LC-BLYP) were investigated. The magnitude of the ZFS from the CASSCF calculations is in good agreement with experiment, whereas the DFT results in varying degrees overestimate the magnitude of the ZFS for both functionals and exhibit a strong functional dependence. It was found in the sampling over the AIMD trajectory that the fluctuations in the transient ZFS tensor derived from DFT are not correlated with those of CASSCF nor does the magnitude of the ZFS from CASSCF and DFT correlate. From the fluctuations in the ZFS tensor, we extract a correlation time of the transient ZFS which is on the sub-picosecond time scale, showing a faster decay than experimental estimates.

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Liquid-state paramagnetic relaxation from first principles

Cited by 9 publications

References 32 publications

Brownian Translational Dynamics on a Flexible Surface: Nuclear Spin Relaxation of Fluid Membrane Phases

Brownian Translational Dynamics on a Flexible Surface: Nuclear Spin Relaxation of Fluid Membrane Phases

Polarization transfer in a spin-exchange optical-pumping experiment

An ab initio CASSCF study of zero field splitting fluctuations in the octet ground state of aqueous [Gd(iii)(HPDO3A)(H2O)]

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