On the calculation of x-ray scattering signals from pairwise radial distribution functions

Dohn, Asmus Ougaard; Biasin, Elisa; Haldrup, Kristoffer; Nielsen, Martin Meedom; Henriksen, Niels Engholm; Møller, Klaus Braagaard

doi:10.1088/0953-4075/48/24/244010

Cited by 44 publications

(43 citation statements)

References 47 publications

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“…As Fig. S2 shows, in the lim- For the isotropic case, ∆S cage was calculated from the RDFs of the solute-solvent atom pairs (Dohn et al, 2015), as further described in the SOI, while it was not necessary to include this term in the analysis of the anisotropic signal, given the good quality of the fit without the inclusion. Finally, ∆S solvent describes the changes arising from the heating of the bulk water and its calculation is detailed in the SOI.…”

Section: Resultsmentioning

confidence: 99%

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

Biasin

Driel

Levi

et al. 2018

J Synchrotron Radiat

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Time-resolved X-ray scattering patterns from photoexcited molecules in solution are in many cases anisotropic at the ultrafast time scales accessible at X-ray free-electron lasers (XFELs). This anisotropy arises from the interaction of a linearly polarized UV-Vis pump laser pulse with the sample, which induces anisotropic structural changes that can be captured by femtosecond X-ray pulses. In this work, a method for quantitative analysis of the anisotropic scattering signal arising from an ensemble of molecules is described, and it is demonstrated how its use can enhance the structural sensitivity of the time-resolved X-ray scattering experiment. This method is applied on time-resolved X-ray scattering patterns measured upon photoexcitation of a solvated di-platinum complex at an XFEL, and the key parameters involved are explored. It is shown that a combined analysis of the anisotropic and isotropic difference scattering signals in this experiment allows a more precise determination of the main photoinduced structural change in the solute, i.e. the change in Pt-Pt bond length, and yields more information on the excitation channels than the analysis of the isotropic scattering only. Finally, it is discussed how the anisotropic transient response of the solvent can enable the determination of key experimental parameters such as the instrument response function.

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Section: Resultsmentioning

confidence: 99%

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

Biasin

Driel

Levi

et al. 2018

J Synchrotron Radiat

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“…These experimentally derived solvation shell signals can be directly compared with the results of the BOMD simulations. Figure 3c shows the difference scattering signal calculated35 from the BOMD simulations at the same 500 fs and 3 ps time delays. The similarity between measured and calculated solvation shell signals provides strong support for guiding the interpretation of the measurements by the structural findings of the simulations.…”

Section: Resultsmentioning

confidence: 99%

Atomistic characterization of the active-site solvation dynamics of a model photocatalyst

et al. 2016

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The interactions between the reactive excited state of molecular photocatalysts and surrounding solvent dictate reaction mechanisms and pathways, but are not readily accessible to conventional optical spectroscopic techniques. Here we report an investigation of the structural and solvation dynamics following excitation of a model photocatalytic molecular system [Ir2(dimen)4]2+, where dimen is para-diisocyanomenthane. The time-dependent structural changes in this model photocatalyst, as well as the changes in the solvation shell structure, have been measured with ultrafast diffuse X-ray scattering and simulated with Born-Oppenheimer Molecular Dynamics. Both methods provide direct access to the solute–solvent pair distribution function, enabling the solvation dynamics around the catalytically active iridium sites to be robustly characterized. Our results provide evidence for the coordination of the iridium atoms by the acetonitrile solvent and demonstrate the viability of using diffuse X-ray scattering at free-electron laser sources for studying the dynamics of photocatalysis.

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“…The ratio between the axial and the equatorial Co-N distances is defined as η. In the LS state the average η is 0.91 (0.88 and 0.92 for the two ligands, with the difference due to the Jahn-Teller effect), while in the HS state η increases to 0.95 (for both ligands).The cage contribution ∆S cage (Q) to the simulated signal was calculated from the Radial Distribution Functions of the solute-solvent atom pairs[32] determined through classical molecular dynamics (MD) simulations[31]. The contribution from changes in the solute structure and solvation cage are related 1:1 and can therefore be combined under the term "structure", ∆S str.…”

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confidence: 99%

Femtosecond X-Ray Scattering Study of Ultrafast Photoinduced Structural Dynamics in Solvated[Co(terpy)2]
Biasin¹,
Driel²,
Kjær³
et al. 2016
Phys. Rev. Lett.
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We study the structural dynamics of photoexcited ½CoðterpyÞ 2 2þ in an aqueous solution with ultrafast x-ray diffuse scattering experiments conducted at the Linac Coherent Light Source. Through direct comparisons with density functional theory calculations, our analysis shows that the photoexcitation event leads to elongation of the Co-N bonds, followed by coherent Co-N bond length oscillations arising from the impulsive excitation of a vibrational mode dominated by the symmetrical stretch of all six Co-N bonds. This mode has a period of 0.33 ps and decays on a subpicosecond time scale. We find that the equilibrium bond-elongated structure of the high spin state is established on a single-picosecond time scale and that this state has a lifetime of ∼7 ps. DOI: 10.1103/PhysRevLett.117.013002 Several Co(II) compounds are known to transition between their low spin (LS) and high spin (HS) electronic states [1][2][3]. Such transitions can be induced by temperature increase, excitation by light, or high magnetic fields [4], and they are accompanied by distinct changes in magnetic and structural properties that may be exploited in the design of display and memory devices [5,6] and in single-molecule spintronic applications [7]. The realization of exploitable spin-state transitions (SSTs) in Co(II) compounds is more challenging than in the corresponding Fe(II) complexes, which have been investigated in great detail during the last decades [8][9][10][11][12][13][14][15]. These challenges stem from the partial occupation of the antibonding e Ã g orbitals in the ground state, which leads to smaller structural changes arising from the SST phenomenon; the corresponding smaller energy barriers between the potential surfaces of the HS and LS Co(II) states result in faster dynamics [1], as well as a high sensitivity to the crystalline environment or to the solvent properties [2]. The key structural parameters for the SSTs are the Co-N bond lengths [8], but the time scales and the dynamics of the LS-HS transitions have remained unclear for Co compounds. Time-resolved x-ray scattering can be used to monitor such structural changes and dynamics if the time resolution of the experiment is sufficiently high. X-ray free electron lasers (XFELs) provide ultrashort (∼30 fs) x-ray pulses and high flux allowing the nuclear dynamics following photoexcitation to be recorded at the required femtosecond time scales [16,17]. Here, we report, for the first time, direct measurements of the excited-state structure and the ultrafast structural dynamics of a solvated Co(II) complex upon a photoinduced SST. Figure 1 shows the molecular structure of ½CoðterpyÞ 2 2þ ðterpy ¼ 2; 2 0 ∶6 0 ; 2 00 − terpyridineÞ. In this six-coordinated complex, the d 7 Co center can be either a LS doublet state or a HS quartet state [2,18]. In solid-state samples, the relative populations of both spin states depend strongly on the In this work, we utilized x-ray diffuse scattering (XDS) laser pump-x-ray probe experiments to study the formation, structure, and decay of...

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On the calculation of x-ray scattering signals from pairwise radial distribution functions

Cited by 44 publications

References 47 publications

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

Atomistic characterization of the active-site solvation dynamics of a model photocatalyst

Femtosecond X-Ray Scattering Study of Ultrafast Photoinduced Structural Dynamics in Solvated[Co(terpy)2]
Biasin¹,
Driel²,
Kjær³
et al. 2016
Phys. Rev. Lett.
Self Cite
96
5
69
0
1
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On the calculation of x-ray scattering signals from pairwise radial distribution functions

Cited by 44 publications

References 47 publications

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

Anisotropy enhanced X-ray scattering from solvated transition metal complexes

Atomistic characterization of the active-site solvation dynamics of a model photocatalyst

Femtosecond X-Ray Scattering Study of Ultrafast Photoinduced Structural Dynamics in Solvated[Co(terpy)2]Biasin1, Driel2, Kjær3 et al. 2016Phys. Rev. Lett.Self Cite9656901View full textAdd to dashboardCite

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Femtosecond X-Ray Scattering Study of Ultrafast Photoinduced Structural Dynamics in Solvated[Co(terpy)2]
Biasin¹,
Driel²,
Kjær³
et al. 2016
Phys. Rev. Lett.
Self Cite
96
5
69
0
1
View full text Add to dashboard Cite