1
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Noguere G, Scotta JP, Xu S, Farhi E, Ollivier J, Calzavarra Y, Rols S, Koza M, Marquez Damian JI. Temperature-dependent dynamic structure factors for liquid water inferred from inelastic neutron scattering measurements. J Chem Phys 2021; 155:024502. [PMID: 34266266 DOI: 10.1063/5.0055779] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Temperature-dependent dynamic structure factors S(Q, ω) for liquid water have been calculated using a composite model, which is based on the decoupling approximation of the mean square displacement of the water molecules into diffusion and solid-like vibrational parts. The solid-like vibrational part Svib(Q, ω) is calculated with the phonon expansion method established in the framework of the incoherent Gaussian approximation. The diffusion part Sdiff(Q, ω) relies on the Egelstaff-Schofield translational diffusion model corrected for jump diffusions and rotational diffusions with the Singwi-Sjölander random model and Sears expansion, respectively. Systematics of the model parameters as a function of temperature were deduced from quasi-elastic neutron scattering data analysis reported in the literature and from molecular dynamics (MD) simulations relying on the TIP4P/2005f model. The resulting S(Q, ω) values are confronted by means of Monte Carlo simulations to inelastic neutron scattering data measured with IN4, IN5, and IN6 time-of-flight spectrometers of the Institut Laue-Langevin (ILL) (Grenoble, France). A modest range of temperatures (283-494 K) has been investigated with neutron wavelengths corresponding to incident neutron energies ranging from 0.57 to 67.6 meV. The neutron-weighted multiphonon spectra deduced from the ILL data indicate a slight overestimation by the MD simulations of the frequency shift and broadening of the librational band. The descriptive power of the composite model was suited for improving the comparison to experiments via Bayesian updating of prior model parameters inferred from MD simulations. The reported posterior temperature-dependent densities of state of hydrogen in H2O would represent valuable insights for studying the collective coupling interactions in the water molecule between the inter- and intramolecular degrees of freedom.
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Affiliation(s)
- G Noguere
- CEA, DES, IRESNE, Cadarache, F-13108 Saint Paul Les Durance, France
| | - J P Scotta
- CEA, DES, IRESNE, Cadarache, F-13108 Saint Paul Les Durance, France
| | - S Xu
- CEA, DES, IRESNE, Cadarache, F-13108 Saint Paul Les Durance, France
| | - E Farhi
- Institut Laue-Langevin, F-38042 Grenoble, France
| | - J Ollivier
- Institut Laue-Langevin, F-38042 Grenoble, France
| | - Y Calzavarra
- Institut Laue-Langevin, F-38042 Grenoble, France
| | - S Rols
- Institut Laue-Langevin, F-38042 Grenoble, France
| | - M Koza
- Institut Laue-Langevin, F-38042 Grenoble, France
| | - J I Marquez Damian
- Neutron Physics Departement and Instituto Balseiro, Centro Atomico Bariloche, CNEA, Bariloche, Argentina
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2
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Martí J, Diaz B. Efficient recursive Adams–Bashforth methods in molecular dynamics simulations of N-body systems interacting through pairwise potentials. MOLECULAR SIMULATION 2020. [DOI: 10.1080/08927022.2020.1815730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Jordi Martí
- Department of Physics, Technical University of Catalonia-Barcelona Tech, Barcelona, Spain
| | - Bernat Diaz
- Faculty of Computer Science, Technical University of Catalonia-Barcelona Tech, Barcelona, Spain
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3
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Taschin A, Bartolini P, Fanetti S, Lapini A, Citroni M, Righini R, Bini R, Torre R. Pressure Effects on Water Dynamics by Time-Resolved Optical Kerr Effect. J Phys Chem Lett 2020; 11:3063-3068. [PMID: 32212735 DOI: 10.1021/acs.jpclett.0c00363] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Despite water being the most common and most widely studied substance in the world, it still presents unknown aspects. In particular, water shows several thermodynamic and dynamical anomalies in the liquid and supercooled metastable phases, and the natures of these phases are still hotly debated. Here, we report measurements of water using the optical Kerr effect as a function of pressure along two isotherms, at 273 K from 0.1 to 750 MPa and at 297 K from 0.1 to 1350 MPa, reaching the supercooled metastable phase. The structural relaxation and the low frequency vibrational dynamics of water show a peculiar pressure dependence similar to that of other dynamical properties. The data analysis suggests the presence in the water phase diagram of a crossover area that divides two regions characterized by different dynamic regimes, which appear to be related to two liquid forms, one dominated by the high density water and the other by the low density water.
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Affiliation(s)
- Andrea Taschin
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - Paolo Bartolini
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - Samuele Fanetti
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
- ICCOM-CNR, Istituto di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Firenze, Italy
| | - Andrea Lapini
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
- INRIM, Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, I-10135 Torino, Italy
| | - Margherita Citroni
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - Roberto Righini
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
- Dipartimento di Chimica "Ugo Schiff", Università di Firenze, via Della Lastruccia 13, I-50019 Sesto Fiorentino, Firenze, Italy
| | - Roberto Bini
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
- ICCOM-CNR, Istituto di Chimica dei Composti OrganoMetallici, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Firenze, Italy
- Dipartimento di Chimica "Ugo Schiff", Università di Firenze, via Della Lastruccia 13, I-50019 Sesto Fiorentino, Firenze, Italy
| | - Renato Torre
- European Laboratory for Non-Linear Spectroscopy (LENS), Università di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
- Dipartimento di Fisica e Astronomia, Università di Firenze, via G. Sansone 1, I-50019 Sesto Fiorentino, Firenze, Italy
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4
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Lu H, Martí J. Binding and dynamics of melatonin at the interface of phosphatidylcholine-cholesterol membranes. PLoS One 2019; 14:e0224624. [PMID: 31697738 PMCID: PMC6837308 DOI: 10.1371/journal.pone.0224624] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 10/17/2019] [Indexed: 12/18/2022] Open
Abstract
The characterization of interactions between melatonin, one main ingredient of medicines regulating sleeping rhythms, and basic components of cellular plasma membranes (phospholipids, cholesterol, metal ions and water) is very important to elucidate the main mechanisms for the introduction of melatonin into cells and also to identify its local structure and microscopic dynamics. Molecular dynamics simulations of melatonin inside mixtures of dimyristoylphosphatidylcholine and cholesterol in NaCl solution at physiological concentration have been performed at 303.15 K to systematically explore melatonin-cholesterol, melatonin-lipid and melatonin-water interactions. Properties such as the area per lipid and thickness of the membrane as well as selected radial distribution functions, binding free energies, angular distributions, atomic spectral densities and translational diffusion of melatonin are reported. The presence of cholesterol significantly affects the behavior of melatonin, which is mainly buried into the interfaces of membranes. Introducing cholesterol into the system helps melatonin change from folded to extended configurations more easily. Our results suggest that there exists a competition between the binding of melatonin to phospholipids and to cholesterol by means of hydrogen-bonds. Spectral densities of melatonin reported in this work, in overall good agreement with experimental data, revealed the participation of each atom of melatonin to its complete spectrum. Melatonin self-diffusion coefficients are of the order of 10-7 cm2/s and they significantly increase when cholesterol is addeed to the membrane.
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Affiliation(s)
- Huixia Lu
- Department of Physics, Technical University of Catalonia-Barcelona Tech. Barcelona, Catalonia, Spain
| | - Jordi Martí
- Department of Physics, Technical University of Catalonia-Barcelona Tech. Barcelona, Catalonia, Spain
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5
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Shiraga K, Tanaka K, Arikawa T, Saito S, Ogawa Y. Reconsideration of the relaxational and vibrational line shapes of liquid water based on ultrabroadband dielectric spectroscopy. Phys Chem Chem Phys 2018; 20:26200-26209. [PMID: 30318523 DOI: 10.1039/c8cp04778b] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Debye relaxation function is widely used to describe the large dielectric dispersion of ambient water around 20 GHz. However, from a theoretical point of view, this function is supposed to give incorrect predictions at high frequencies owing to the inappropriate assumption that inertial effects and intermolecular interactions do not affect the relaxation dynamics. Our ultrabroadband spectroscopy investigation of liquid water ranging from 500 MHz to 400 THz did demonstrate that the Debye function is inaccurate far above the microwave region. As an alternative, we tried a stochastic frequency modulation (SFM) model assuming instantaneous modification of the line shapes by the correlation with the surrounding system. The SFM relaxation model reproduced the experimental dielectric spectra up to 400 THz, showing that the hydrogen-bond dynamics are associated with the inertial effect that causes the non-exponential relaxation behaviour in a very short time (typically 25 fs). Within the framework of this relaxation model, the hindered translation modes are able to be approximated as fast modulation (homogeneous) line shapes because the interaction time with frequency modulation is too short. Compared with them, the libation mode is found to have a relatively slow modulation (inhomogeneous) origin, where disturbance of water hydrogen bonds induced by the hindered translations leads to fluctuations in the libration frequency.
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Affiliation(s)
- Keiichiro Shiraga
- RIKEN Center for Integrative Medical Sciences, Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan.
| | - Koichiro Tanaka
- Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan. and Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Takashi Arikawa
- Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
| | - Shinji Saito
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Myodaiji, Okazaki, Aichi 444-8585, Japan. and The Graduate University for Advanced Studies, Myodaiji, Okazaki, Aichi 444-8585, Japan
| | - Yuichi Ogawa
- Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
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6
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Lunkenheimer P, Emmert S, Gulich R, Köhler M, Wolf M, Schwab M, Loidl A. Electromagnetic-radiation absorption by water. Phys Rev E 2017; 96:062607. [PMID: 29347319 DOI: 10.1103/physreve.96.062607] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Indexed: 06/07/2023]
Abstract
Why does a microwave oven work? How does biological tissue absorb electromagnetic radiation? Astonishingly, we do not have a definite answer to these simple questions because the microscopic processes governing the absorption of electromagnetic waves by water are largely unclarified. This absorption can be quantified by dielectric loss spectra, which reveal a huge peak at a frequency of the exciting electric field of about 20 GHz and a gradual tailing off toward higher frequencies. The microscopic interpretation of such spectra is highly controversial and various superpositions of relaxation and resonance processes ascribed to single-molecule or molecule-cluster motions have been proposed for their analysis. By combining dielectric, microwave, THz, and far-infrared spectroscopy, here we provide nearly continuous temperature-dependent broadband spectra of water. Moreover, we find that corresponding spectra for aqueous solutions reveal the same features as pure water. However, in contrast to the latter, crystallization in these solutions can be avoided by supercooling. As different spectral contributions tend to disentangle at low temperatures, this enables us to deconvolute them when approaching the glass transition under cooling. We find that the overall spectral development, including the 20 GHz feature (employed for microwave heating), closely resembles the behavior known for common supercooled liquids. Thus water's absorption of electromagnetic waves at room temperature is not unusual but very similar to that of glass-forming liquids at elevated temperatures, deep in the low-viscosity liquid regime, and should be interpreted along similar lines.
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Affiliation(s)
- P Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - S Emmert
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - R Gulich
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - M Köhler
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - M Wolf
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - M Schwab
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
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7
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Taschin A, Bartolini P, Eramo R, Righini R, Torre R. Optical Kerr effect of liquid and supercooled water: the experimental and data analysis perspective. J Chem Phys 2015; 141:084507. [PMID: 25173021 DOI: 10.1063/1.4893557] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The time-resolved optical Kerr effect spectroscopy (OKE) is a powerful experimental tool enabling accurate investigations of the dynamic phenomena in molecular liquids. We introduced innovative experimental and fitting procedures, that enable a safe deconvolution of sample response function from the instrumental function. This is a critical issue in order to measure the dynamics of liquid water. We report OKE data on water measuring intermolecular vibrations and the structural relaxation processes in an extended temperature range, inclusive of the supercooled states. The unpreceded data quality makes possible a solid comparison with few theoretical models: the multi-mode Brownian oscillator model, the Kubo's discrete random jump model, and the schematic mode-coupling model. All these models produce reasonable good fits of the OKE data of stable liquid water, i.e., over the freezing point. The features of water dynamics in the OKE data becomes unambiguous only at lower temperatures, i.e., for water in the metastable supercooled phase. We found that the schematic mode-coupling model provides the more rigorous and complete model for water dynamics, even if its intrinsic hydrodynamic approach does not give a direct access to the molecular information.
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Affiliation(s)
- A Taschin
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - P Bartolini
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - R Eramo
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - R Righini
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - R Torre
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
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8
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Guardia E, Skarmoutsos I, Masia M. Hydrogen Bonding and Related Properties in Liquid Water: A Car–Parrinello Molecular Dynamics Simulation Study. J Phys Chem B 2014; 119:8926-38. [DOI: 10.1021/jp507196q] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Elvira Guardia
- Departament
de Física i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Campus Nord B4−B5, Barcelona 08034, Spain
| | - Ioannis Skarmoutsos
- Departament
de Física i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Campus Nord B4−B5, Barcelona 08034, Spain
- INAC/SPrAM (UMR 5819 UJF, CNRS, CEA), CEA-Grenoble, 17 Rue des Martyrs, 38054 Grenoble, France
| | - Marco Masia
- Dipartimento
di Chimica e Farmacia, Universita degli Studi di Sassari, Istituto Officina dei Materiali del
CNR, UOS SLACS, Via Vienna 2, 07100 Sassari, Italy
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9
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Taschin A, Bartolini P, Eramo R, Righini R, Torre R. Evidence of two distinct local structures of water from ambient to supercooled conditions. Nat Commun 2014; 4:2401. [PMID: 24029922 DOI: 10.1038/ncomms3401] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 08/05/2013] [Indexed: 12/29/2022] Open
Abstract
The liquid and supercooled states of water show a series of anomalies whose nature is debated. A key role is attributed to the formation of structural aggregates induced by critical phenomena occurring deep in the supercooled region; the nature of the water anomalies and of the hidden critical processes remains elusive. Here we report a time-resolved optical Kerr effect investigation of the vibrational dynamics and relaxation processes in supercooled bulk water. The experiment measures the water intermolecular vibrations and the structural relaxation process in an extended temperature range, and with unprecedented data quality. A mode-coupling analysis of the experimental data enables to characterize the intermolecular vibrational modes and their interplay with the structural relaxation process. The results bring evidence of the coexistence of two local configurations, which are interpreted as high-density and low-density water forms, with an increasing weight of the latter at low temperatures.
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Affiliation(s)
- A Taschin
- European Lab for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, Sesto Fiorentino, I-50019 Firenze, Italy
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10
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Wan Q, Spanu L, Galli GA, Gygi F. Raman Spectra of Liquid Water from Ab Initio Molecular Dynamics: Vibrational Signatures of Charge Fluctuations in the Hydrogen Bond Network. J Chem Theory Comput 2013; 9:4124-30. [PMID: 26592405 DOI: 10.1021/ct4005307] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
We report the first ab initio simulations of the Raman spectra of liquid water, obtained by combining first principles molecular dynamics and density functional perturbation theory. Our computed spectra are in good agreement with experiments, especially in the low frequency region. We also describe a systematic strategy to analyze the Raman intensities, which is of general applicability to molecular solids and liquids, and it is based on maximally localized Wannier functions and effective molecular polarizabilities. Our analysis revealed the presence of intermolecular charge fluctuations accompanying the hydrogen bond (HB) stretching modes at 270 cm(-1), in spite of the absence of any Raman activity in the isotropic spectrum. We also found that charge fluctuations partly contribute to the 200 cm(-1) peak in the anisotropic spectrum, thus providing insight into the controversial origin of such peak. Our results highlighted the importance of taking into account electronic effects in interpreting the Raman spectra of liquid water and the key role of charge fluctuations within the HB network; they also pointed at the inaccuracies of models using constant molecular polarizabilities to describe the Raman response of liquid water.
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Affiliation(s)
- Quan Wan
- Department of Chemistry, University of California , Davis, California 95616, United States
| | - Leonardo Spanu
- Department of Chemistry, University of California , Davis, California 95616, United States
| | - Giulia A Galli
- Department of Chemistry, University of California , Davis, California 95616, United States.,Department of Physics, University of California , Davis, California 95616, United States, and
| | - François Gygi
- Department of Computer Science, University of California , Davis, California 95616, United States
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11
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Taschin A, Bartolini P, Marcelli A, Righini R, Torre R. A comparative study on bulk and nanoconfined water by time-resolved optical Kerr effect spectroscopy. Faraday Discuss 2013; 167:293-308. [DOI: 10.1039/c3fd00060e] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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12
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Turton DA, Corsaro C, Martin DF, Mallamace F, Wynne K. The dynamic crossover in water does not require bulk water. Phys Chem Chem Phys 2012; 14:8067-73. [DOI: 10.1039/c2cp40703e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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13
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The Extreme Low-Frequency Raman Spectrum of Liquid Water. Chemphyschem 2011; 12:913-4. [DOI: 10.1002/cphc.201000894] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Revised: 02/09/2011] [Indexed: 11/07/2022]
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14
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Rodriguez J, Laria D, Guàrdia E, Martí J. Dynamics of water nanodroplets and aqueous protons in non-ionic reverse micelles. Phys Chem Chem Phys 2009; 11:1484-90. [PMID: 19240924 DOI: 10.1039/b816827j] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present a study of the microscopic dynamics of water trapped in reverse non-ionic micelles by means of a series of molecular dynamics simulations. The analysis of the effects of micellar confinement on spectroscopical properties of an excess proton has also been considered. Our micelles were microemulsions made with the neutral surfactant diethylene glycol monodecyl ether [CH(3)(CH(2))(11)(OC(2)H(4))(2)OH]. Simulation experiments including the proton species were performed using a multistate empirical valence bond Hamiltonian model. Diffusion of water in the micelle is markedly slower than that in the bulk liquid, in the same fashion as happens with reorientational dynamics. Spectral densities of hydrogens revealed a blue-shift of the OH-stretching vibration together with a split of the main band into two components. Absorption lineshapes of the solvated proton in the vicinity of the internal surface of the micelle indicate the coexistence of Eigen-like and Zundel-like structures and a tendency to red-shifting (compared to the aqueous unconstrained excess proton case) of the two relevant spectral bands (around 2000 and 2500 wavenumbers) mainly due to the slower dynamics of proton vibrations in water near interfaces.
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Affiliation(s)
- J Rodriguez
- Departamento de Química Inorgánica, Analítica y Química-Física, e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, 1428, Argentina
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15
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Elola MD, Ladanyi BM. Intermolecular polarizability dynamics of aqueous formamide liquid mixtures studied by molecular dynamics simulations. J Chem Phys 2007; 126:084504. [PMID: 17343455 DOI: 10.1063/1.2446782] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
A molecular dynamics simulation study is presented for the relaxation of the polarizability anisotropy in liquid mixtures of formamide and water, using a dipolar induction scheme that involves the intrinsic polarizability and first hyperpolarizability tensors of the molecules, and the dipole-quadrupole polarizability of water species. The long time diffusive decay of the collective polarizability anisotropy correlations exhibits a substantial slowing down as the formamide mole fraction increases in the mixture. The diffusive times for the polarizability relaxation obtained from the authors' simulations are in good agreement with optical Kerr effect experimental data, and they are found to correlate nearly linearly with the estimated mean lifetimes of the hydrogen bonds within the mixture, suggesting that the relaxation of the hydrogen bond network is responsible to some extent for the collective relaxation of the polarizability anisotropy of the mixture. The short time behavior of the polarizability anisotropy relaxation was investigated by computing the nuclear response function, R(t), which is very rapidly dominated by the formamide contribution as it is added to water, due to the much larger polarizability anisotropy of formamide molecules compared to that of water. Several contributions to the Raman spectrum were also analyzed as a function of composition, and the dynamical origin of the different bands was determined.
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Affiliation(s)
- M Dolores Elola
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
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16
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Tsai K, Wu TM. Local structural effects on low-frequency vibrational spectrum of liquid water: The instantaneous-normal-mode analysis. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2005.10.067] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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17
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Lisichkin Y, Saharova L, Marti J, Novikov A. Temperature dependence of the generalized frequency distribution of water molecules: comparison of experiments and molecular dynamics simulations. MOLECULAR SIMULATION 2005. [DOI: 10.1080/08927020500411930] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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18
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Suzuki T, Kawashima H, Kotoku H, Sota T. Structural Fluctuation and Dynamics of Ribose Puckering in Aqueous Solution from First Principles. J Phys Chem B 2005; 109:12997-3005. [PMID: 16852613 DOI: 10.1021/jp050475i] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using the method of ab initio molecular dynamics, we examine the structural fluctuation and the low-frequency dynamics of beta-ribofuranose puckering in aqueous solution. Our analysis suggests that the distance between the anomeric and hydroxymethyl oxygens is a simple relevant geometrical parameter that dynamically correlates with the phase angle in the north region. The time-frequency analysis using the Hilbert-Huang transform also confirms the correlation, and most of the instantaneous frequencies for the phase angle and the above distance are found to be concentrated on the region below about 100 cm(-1). Our analysis of ab initio molecular dynamics trajectories suggests that the molecular origin of the hydration effects on the low-frequency dynamics of beta-ribofuranose puckering is closely related to this correlation and thus primarily attributed to the relatively local interactions among the anomeric and hydroxymethyl oxygens and the surrounding water molecules near them. Additionally, we discuss the difference in the low-frequency dynamics of beta-ribofuranose puckering between two hydroxymethyl rotamers.
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Affiliation(s)
- Teppei Suzuki
- Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.
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Padró JÀ, Martı́ J. Response to “Comment on ‘An interpretation of the low-frequency spectrum of liquid water’ ” [J. Chem. Phys. 118, 452 (2003)]. J Chem Phys 2004. [DOI: 10.1063/1.1634252] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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