Simulations of electric field gradient fluctuations and dynamics around sodium ions in ionic liquids

Article Article scientifique Article Simulations of electric field gradient fluctuations and dynamics around sodium ions in ionic liquids eng 2022-12-22 2022 author Gimbal-Zofka Yann Gaël Geneva U. 807206 author Karg Béatrice Geneva U. 929588 author Dziubinska-Kühn Katarzyna CERN author Kowalska Magdalena CERN 915535 Département de physique nucléaire et corpusculaire (FINUC) author Wesolowski Tomasz Adam Geneva U. 92358 Département de chimie physique (CHIFI) author Rumble Christopher Allen Penn State U., Altoona 877558 1-11 244502 10.1063/5.0126693 36586985 0021-9606 https://pubs.aip.org/jcp/article/157/24/244502/2842952/Simulations-of-electric-field-gradient The T1 relaxation time measured in nuclear magnetic resonance experiments contains information about electric field gradient (EFG) fluctuations around a nucleus, but computer simulations are typically required to interpret the underlying dynamics. This study uses classical molecular dynamics (MD) simulations and quantum chemical calculations, to investigate EFG fluctuations around a Na+ ion dissolved in the ionic liquid 1-ethyl 3-methylimidazolium tetrafluoroborate, [Im21][BF4], to provide a framework for future interpretation of NMR experiments. Our calculations demonstrate that the Sternheimer approximation holds for Na+ in [Im21][BF4], and the anti-shielding coefficient is comparable to its value in water. EFG correlation functions, CEFG(t), calculated using quantum mechanical methods or from force field charges are roughly equivalent after 200 fs, supporting the use of classical MD for estimating T1 times of monatomic ions in this ionic liquid. The EFG dynamics are strongly bi-modal, with 75%–90% of the de-correlation attributable to inertial solvent motion and the remainder to a highly distributed diffusional processes. Integral relaxation times, ⟨τEFG⟩, were found to deviate from hydrodynamic predictions and were non-linearly coupled to solvent viscosity. Further investigation showed that Na+ is solvated by four tetrahedrally arranged [BF4]- anions and directly coordinated by ∼6 fluorine atoms. Exchange of [BF4]- anions is rare on the 25–50 ns timescale and suggests that motion of solvent-shell [BF4]- is the primary mechanism for the EFG fluctuations. Different couplings of [BF4]- translational and rotational diffusion to viscosity are shown to be the source of the non-hydrodynamic scaling of ⟨τEFG⟩. Dewey 540 Dewey 500.2 European Commission Ultra-sensitive NMR in liquids 640645 BetaDropNMR EU H2020 38 Département de chimie physique 142 34 Département de physique nucléaire et corpusculaire 132 false The Journal of chemical physics 157 24 198a501f-f3ea-4ed4-afd1-3078af751ddc Article (Published version) Public Article_scientifique_from_crossref-.pdf 5340516 application/pdf 526f342d23115cf65ce8f9ad687e0dd838bec5d0ca41b2db4179a67287d117f0 openAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie physique Faculté des sciences / Section de physique / Département de physique nucléaire et corpusculaire

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Simulations of electric field gradient fluctuations and dynamics around sodium ions in ionic liquids	The Journal of chemical physics	2022	69	167

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Gimbal-Zofka, Yann Gaël

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