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Biswas A, Mallik BS. Direct Correlation between Short-Range Vibrational Spectral Diffusion and Localized Ion-Cage Dynamics of Water-in-Salt Electrolytes. J Phys Chem B 2023; 127:236-248. [PMID: 36575973 DOI: 10.1021/acs.jpcb.2c04391] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The molecular dynamics simulations of a "water-in-salt" electrolyte, lithium bis(trifluoromethyl sulfonyl) imide (LiNTf2), with a varying concentration range of 3 to 20 m were performed to establish a direct connection between a dynamic property like the ion-cage lifetime with the short-range vibrational stretching frequency shift of the used probe, HOD. The properties reported here are compared to that obtained from experiments performed at the same concentrations. The time-series wavelet transform was adopted as a preferable mathematical tool for calculating the instantaneous fluctuating frequencies of the probe O-D stretch mode and the concentration-dependent vibrational stretch spectral signature based on the variable functions associated with a particular chemical bond derived from classical molecular dynamics trajectories. The decay time constants of frequency fluctuations and the lifetime of the ion cage (τIC) were estimated as a function of salt concentration. Herein, we emphasize the correlation between the slowest time constant (τ3) of the decay of O-D stretch frequency fluctuations and the timescales associated with the lifetime of ion cages (τIC). The results exhibit that the existing relationships were also concentration-dependent. Therefore, this study highlights the connection between the ionic motions that regulate the overall system dynamics with the short-range vibrational frequency shift of the used probe, which was used similar to experiments. It also provides an understanding of the interionic interactions and the dynamical and spectral properties of the electrolytic mixtures. We establish a direct correlation between short-range frequency profile and localized ion-cage lifetime, which can fill the gap of understanding between viscosity, vibrational frequency, and ion-cage dynamics of electrolytes.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
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Biswas A, Mallik BS. Molecular Simulation-Guided Spectroscopy of Imidazolium-Based Ionic Liquids and Effects of Methylation on Ion-Cage and -Pair Dynamics. J Phys Chem B 2022; 126:8838-8850. [PMID: 36264223 DOI: 10.1021/acs.jpcb.2c04901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Classical molecular dynamics simulations were performed to assess an atomistic interpretation of the ion-probe structural interactions in two typical ionic liquids (ILs), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIm][NTf2] and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide [BDimIm][NTf2] through computational ultrafast spectroscopy. The nitrile stretching vibrations of the thiocyanate anion, [SCN]-, serve as the local mode of the ultrafast system dynamics within the imidazolium-based ionic liquid environment. The wavelet transform of classical trajectories determines the time-varying fluctuating frequencies and the stretch spectral signatures of SCN- in the normalized distribution. However, computational modeling of the two-dimensional (2D) spectra from the wavelet-derived vibrational frequencies yields time evolution of the local molecular structure along with the varied time-dependent dynamics of the spectral diffusion process. We calculated the frequency-frequency correlation functions (FFCFs), time correlations associated with the ion-pair and -cage dynamics, and mean square displacements as a function of time, depicting diffusive dynamics. The calculated results based on the pair correlation functions and the distribution of atomic density suggest that the hydrogen and methylated carbon at the two-position of the imidazolium ring of [BMIm] and [BDimIm] cations, respectively, strongly interact with the probe through the N of the thiocyanate anion rather than the S atom. The center-of-mass center-of-mass (COM-COM) cation-probe radial distribution functions (RDFs) in conjunction with the site-specific structural analysis further reveal well-structured interactions of the thiocyanate ion and [BMIm]+ cation rather than the [BDimIm] cation. In contrast, the anion-probe COM-COM RDFs depict weak interactive associations within the vibrational probe [SCN]- and [NTf2]- ions. Methylation at the two-position of the imidazolium ring predicts slower structural reorganization and breaking and reformation dynamics of the ion pairs and cages within the ionic liquid framework.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy502285, Telangana, India
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Biswas A, Mallik BS. Multiple Ensembles of the Hydrogen-bonded Network in Ethylammonium Nitrate versus Water from Vibrational Spectral Dynamics of SCN- Probe. Chemphyschem 2022; 23:e202200497. [PMID: 35965410 DOI: 10.1002/cphc.202200497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 08/05/2022] [Indexed: 11/12/2022]
Abstract
We performed classical molecular dynamics simulations to monitor the structural interactions and ultrafast dynamical and spectral response in the protic ionic liquid, ethylammonium nitrate (EAN) and water using the nitrile stretching mode of thiocyanate ion (SCN-) as the vibrational probe. The normalized stretch frequency distribution of nitrile stretch of SCN- attains an asymmetric shape in EAN, indicating the existence of more than one hydrogen-bonding environment in EAN. We computed the 2D IR spectrum from classical trajectories, applying the response function formalism. Spectral diffusion dynamics in EAN undergo an initial rattling of the SCN - inside the local ion-cage occurring at a timescale of 0.10 ps, followed by the breakup of the ion-cage activating molecular diffusion at 7.86 ps timescale. In contrast, the dynamics of structural reorganization occur at a timescale of 0.58 ps in H 2 O. Hence, the time dependence of the frequency-frequency correlation function decay hints at the local molecular structure and ultrafast ion dynamics of the SCN - probe. The loss of frequency correlation read from the peak shape changes in the 2D correlation spectrum as a function of waiting time is faster in H 2 O than in EAN due to the enhanced structural ordering and higher viscosity of the latter. We provide an atomic-level interpretation of the solvation environment around SCN - in EAN and water, which indicates the multiple ensembles of the hydrogen bond network in EAN.
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Affiliation(s)
- Aritri Biswas
- IITH: Indian Institute of Technology Hyderabad, Chemistry, INDIA
| | - Bhabani S Mallik
- IITH: Indian Institute of Technology Hyderabad, Chemistry, Kandi, 502285, Sangareddy, INDIA
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Biswas A, Mallik BS. Ionic Dynamics and Vibrational Spectral Diffusion of a Protic Alkylammonium Ionic Salt through Intrinsic Cationic N-H Vibrational Probe from FPMD Simulations. J Phys Chem A 2022; 126:5134-5147. [PMID: 35900106 DOI: 10.1021/acs.jpca.2c03387] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We employed density functional theory (DFT)-based molecular dynamics simulations to explore the structure, dynamics, and spectral properties of the protic ionic entity trimethylammonium chloride (TMACl). Structural investigations include calculating the site-site radial distribution functions (RDFs), the distribution of constituent cations and anions in three-dimensional space, and combined distribution functions of the hydrogen-bonded pair RDF versus angle, revealing the structural characteristics of the ionic solvation and the intermolecular interactions within ions. Further, we determined the instantaneous vibrational stretching frequencies of the intrinsic N-H stretch probe modes by applying the time-series wavelet method. The associated ionic dynamics within the protic ionic compound were investigated by calculating the time-evolution of the fluctuating frequencies and the frequency-time correlation functions (FFCFs). The time scale related to the local structural relaxation process and the average hydrogen bond lifetime, ion cage dynamics, and mean squared displacement were investigated. The faster decay component of the FFCFs, depicting the intermolecular motion of intact hydrogen bonds in TMACl, is 0.07 ps for the Perdew-Burke-Ernzerhof (PBE)-based simulation and 0.06 ps for the PBE-D2 representation. The slower time scale of the longer picosecond decay time component of PBE and PBE-D2 representations are 3.13 and 2.87 ps, respectively. These picosecond time scales represent more significant fluctuations of the hydrogen-bonding partners in the ionic entity and hydrogen-bond jump events accompanied by large angular jumps. The longest picosecond time scales represent structural relaxation, including large angular jumps and ion-pair dynamics. Also, ion cage lifetimes correlate with the slowest time scale of the associated dynamics of vibrational spectral diffusion despite the type of DFT functional. This study benchmarks DFT treatments of the exchange-correlation functional with and without the van der Waals (vdW) dispersion correction scheme. The inclusion of vdW interactions to the PBE functional represents a less structured state of the ionic entity and faster dynamics of the molecular motions relative to the one predicted by the PBE system. All the results illustrate the necessity of accurately describing the Coulomb interactions, vdW dispersive interactive forces, and localized hydrogen bonds required to sustain the energetic balance in this ionic salt.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502284, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502284, Telangana, India
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Biswas A, Mallik BS. Microheterogeneity-Induced Vibrational Spectral Dynamics of Aqueous 1-Alkyl-3-methylimidazolium Tetrafluoroborate Ionic Liquids of Different Cationic Chain Lengths. J Phys Chem B 2022; 126:5523-5533. [PMID: 35833870 DOI: 10.1021/acs.jpcb.2c03561] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have monitored the impacts of an increment in the alkyl chain length of the imidazolium-based tetrafluoroborate ionic liquids on the local deuteroxyl probe modes of interest. For this study, we have taken 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIm][BF4], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIm][BF4], 1-octyl-3-methylimidazolium tetrafluoroborate [OMIm][BF4], and 1-decyl-3-methylimidazolium tetrafluoroborate [DMIm][BF4] ionic liquid solutions with 5% HOD in H2O as the vibrational reporter of the associated ultrafast system dynamics. Classical molecular dynamics (MD) simulations were employed to determine molecular structure and dynamic properties, while the spectral profiles were derived by applying the wavelet analysis of classical trajectories. Spatial distribution functions reveal the heterogeneity within the molecular structures of the ionic liquids (ILs) with varying alkyl chain lengths. The intense position of the spectral peak, the frequency corresponding to the shoulder peak, and the spectral linewidth of the O-D stretch distribution are not influenced by the increment in the cationic chain length. In addition, the ionic liquid (IL) [BMIm][BF4] exhibits a notable trend; the dynamic timescales are longer than the other studied systems. Therefore, we have performed the Voronoi decomposition analysis of the ionic and the polar-apolar domains, symmetrically increasing the length of alkyl chains on the IL cations. Domain analysis reveals structural microheterogeneity; the anions form discrete domains, and the ionic liquid constituting cations form continuous domains irrespective of the alkyl chain length on the imidazolium cations. Therefore, this computational ultrafast spectroscopy study aids in forming a molecular-level picture of the ionic liquid cations and anions in the liquid phase, providing a detailed interpretation of the spectral properties of the probe stretching vibrations.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
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Dereka B, Lewis NHC, Zhang Y, Hahn NT, Keim JH, Snyder SA, Maginn EJ, Tokmakoff A. Exchange-Mediated Transport in Battery Electrolytes: Ultrafast or Ultraslow? J Am Chem Soc 2022; 144:8591-8604. [PMID: 35470669 DOI: 10.1021/jacs.2c00154] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding the mechanisms of charge transport in batteries is important for the rational design of new electrolyte formulations. Persistent questions about ion transport mechanisms in battery electrolytes are often framed in terms of vehicular diffusion by persistent ion-solvent complexes versus structural diffusion through the breaking and reformation of ion-solvent contacts, i.e., solvent exchange events. Ultrafast two-dimensional (2D) IR spectroscopy can probe exchange processes directly via the evolution of the cross-peaks on picosecond time scales. However, vibrational energy transfer in the absence of solvent exchange gives rise to the same spectral signatures, hiding the desired processes. We employ 2D IR on solvent resonances of a mixture of acetonitrile isotopologues to differentiate chemical exchange and energy-transfer dynamics in a comprehensive series of Li+, Mg2+, Zn2+, Ca2+, and Ba2+ bis(trifluoromethylsulfonyl)imide electrolytes from the dilute to the superconcentrated regime. No exchange phenomena occur within at least 100 ps, regardless of the ion identity, salt concentration, and presence of water. All of the observed spectral dynamics originate from the intermolecular energy transfer. These results place the lower experimental boundary on the ion-solvent residence times to several hundred picoseconds, much slower than previously suggested. With the help of MD simulations and conductivity measurements on the Li+ and Zn2+ systems, we discuss these results as a continuum of vehicular and structural modalities that vary with concentration and emphasize the importance of collective electrolyte motions to ion transport. These results hold broadly applicable to many battery-relevant ions and solvents.
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Affiliation(s)
- Bogdan Dereka
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States.,Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Nicholas H C Lewis
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States.,Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Yong Zhang
- Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Nathan T Hahn
- Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Material, Physical and Chemical Sciences Center, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Jonathan H Keim
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Scott A Snyder
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Edward J Maginn
- Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States.,Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Andrei Tokmakoff
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States.,Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States.,Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States.,Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States
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Biswas A, Mallik BS. Vibrational Spectral Dynamics and Ion-Probe Interactions of the Hydrogen-Bonded Liquids in 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Chem Phys 2022. [DOI: 10.1016/j.chemphys.2022.111519] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Biswas A, Mallik BS. 2D IR spectra of the intrinsic vibrational probes of ionic liquid from dispersion corrected DFT-MD simulations. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.118390] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Biswas A, Mallik BS. Revisiting OD-stretching dynamics of methanol‑d4, ethanol-d6 and dilute HOD/H2O mixture with predefined potentials and wavelet transform spectra. Chem Phys 2022. [DOI: 10.1016/j.chemphys.2021.111385] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Triolo A, Di Lisio V, Lo Celso F, Appetecchi GB, Fazio B, Chater P, Martinelli A, Sciubba F, Russina O. Liquid Structure of a Water-in-Salt Electrolyte with a Remarkably Asymmetric Anion. J Phys Chem B 2021; 125:12500-12517. [PMID: 34738812 PMCID: PMC9282637 DOI: 10.1021/acs.jpcb.1c06759] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Water-in-salt
systems, i.e., super-concentrated aqueous electrolytes,
such as lithium bis(trifluoromethanesulfonyl)imide (21 mol/kgwater), have been recently discovered to exhibit unexpectedly
large electrochemical windows and high lithium transference numbers,
thus paving the way to safe and sustainable charge storage devices.
The peculiar transport features in these electrolytes are influenced
by their intrinsically nanoseparated morphology, stemming from the
anion hydrophobic nature and manifesting as nanosegregation between
anions and water domains. The underlying mechanism behind this structure–dynamics
correlation is, however, still a matter of strong debate. Here, we
enhance the apolar nature of the anions, exploring the properties
of the aqueous electrolytes of lithium salts with a strongly asymmetric
anion, namely, (trifluoromethylsulfonyl)(nonafluorobutylsulfonyl)
imide. Using a synergy of experimental and computational tools, we
detect a remarkable level of structural heterogeneity at a mesoscopic
level between anion-rich and water-rich domains. Such a ubiquitous
sponge-like, bicontinuous morphology develops across the whole concentration
range, evolving from large fluorinated globules at high dilution to
a percolating fluorous matrix intercalated by water nanowires at super-concentrated
regimes. Even at extremely concentrated conditions, a large population
of fully hydrated lithium ions, with no anion coordination, is detected.
One can then derive that the concomitant coexistence of (i) a mesoscopically
segregated structure and (ii) fully hydrated lithium clusters disentangled
from anion coordination enables the peculiar lithium diffusion features
that characterize water-in-salt systems.
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Affiliation(s)
- Alessandro Triolo
- Laboratorio Liquidi Ionici, Istituto Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM-CNR), Rome 00133, Italy
| | - Valerio Di Lisio
- Department of Chemistry, University of Rome Sapienza, Rome 00185, Italy
| | - Fabrizio Lo Celso
- Laboratorio Liquidi Ionici, Istituto Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM-CNR), Rome 00133, Italy.,Department of Physics and Chemistry, Università di Palermo, Palermo 90133, Italy
| | | | - Barbara Fazio
- Istituto Processi Chimico-Fisici, Consiglio Nazionale delle Ricerche (IPCF-CNR), Messina 98158, Italy
| | - Philip Chater
- Diamond House, Harwell Science & Innovation Campus, Diamond Light Source, Ltd., Didcot OX11 0DE, U.K
| | - Andrea Martinelli
- Department of Chemistry, University of Rome Sapienza, Rome 00185, Italy
| | - Fabio Sciubba
- Department of Chemistry, University of Rome Sapienza, Rome 00185, Italy.,NMR-Based Metabolomics Laboratory (NMLab), Sapienza University of Rome, Rome 00185, Italy
| | - Olga Russina
- Laboratorio Liquidi Ionici, Istituto Struttura della Materia, Consiglio Nazionale delle Ricerche (ISM-CNR), Rome 00133, Italy.,Department of Chemistry, University of Rome Sapienza, Rome 00185, Italy
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Biswas A, Mallik BS. Dynamics of Ionic Liquid through Intrinsic Vibrational Probes Using the Dispersion-Corrected DFT Functionals. J Phys Chem B 2021; 125:6994-7008. [PMID: 34142827 DOI: 10.1021/acs.jpcb.1c04960] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
First principles molecular dynamics simulations have been utilized to study the spectral properties of the protic ionic liquid, methylammonium formate (MAF). All simulations were performed using density functional theory (DFT) and various van der Waals-corrected exchange-correlation functionals. We calculated the vibrational stretch frequency distributions, determined the time-frequency correlations of the intrinsic vibrational probes, the N-H and C-O modes in MAF, and the frequency-structure correlations. We also estimated the average hydrogen-bond lifetimes and orientation dynamics to capture the ultrafast spectral response. The spectroscopic signature of the N-H stretching vibrations using the Becke-Lee-Yang-Parr (BLYP) and Perdew-Burke-Ernzerhof (PBE) functionals displays a spectral shift in the lower frequency side, suggesting stronger hydrogen-bonding interactions represented by the gradient approximation functionals than the van der Waals (vdW)-corrected simulations. The carboxylate frequency profiles with the dispersion-corrected representations are almost similar without a significant difference in the normalized distributions. Besides, the COO stretching frequencies at the peak maxima positions of the PBE functionals exhibit a lesser deviation from the experimental data. Spectral diffusion dynamics of the intrinsic vibrational probes on the cationic and anionic sites of the ionic liquid proceed through a short time relaxation of the intact hydrogen bonds followed by an intermediate time constant and a longer time decay indicating the switchover of hydrogen bonds. Dispersion-corrected atom-centered one-electron potential (DCACP) correction added to the BLYP system slows down the picosecond time scales of frequency correlation and the time constants of rotational motion, lengthening the overall system dynamics. The observed trends in the time-dependent decays of frequency fluctuations and the orientation autocorrelation functions correlate with the structural interactions in liquid MAF and hydrogen-bond dynamics. In this study, we examine the predictions made by different density functional treatments comparing the results of the uncorrected BLYP and PBE representations with the semiempirical vdW methods of Grimme and matching our calculated data with the experimental observations.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
| | - Bhabani S Mallik
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy 502285, Telangana, India
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Biswas A, Mallik BS. Conformation-induced vibrational spectral dynamics of hydrogen peroxide and vicinal water molecules. Phys Chem Chem Phys 2021; 23:6665-6676. [PMID: 33710191 DOI: 10.1039/d0cp06028c] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We studied the conformation-induced spectral response of water molecules due to site-specific structural alterations of solvated hydrogen peroxide (H2O2) employing DFT-based first principles molecular dynamics (FPMD) simulations. Wavelet transform was used to determine the time-dependent frequencies of the hydroxyls of water molecules and the O-H stretch modes of H2O2. Shifts in the vibrational frequency of the hydrogen-bonded hydroxyls inside the solvation shell of H2O2 support multiple distinctive hydrogen bonding environments. This paper classifies two distinct hydrogen bond types inside the O-OW solvation shell of H2O2, and the dynamical calculations provide a quantitative estimation of the relative hydrogen bond strength. We ascertain the reason for not observing the escape of water molecules from the hydrogen peroxide hydration shell, unlike the solvation shell of ionic solutions and neutral solutes. Besides, we provide a comprehensive analysis of the spectral shifts in the normalized frequency distribution, the time-dependent decay of frequency-frequency correlation functions, and the hydrogen bond length scale fluctuations. We also quantify the relative contribution of the cisoid and transoid conformers affecting the vibrational spectral signature of the vicinal water molecules. While the transoid conformers promote the hydrogen bonding interactions through the oxygen site (OHW), the cisoid conformers facilitate hydrogen peroxide-water hydrogen bond formation through the hydrogen site (HOW). These non-identical hydrogen bond associations stabilize hydrogen peroxide in water.
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Affiliation(s)
- Aritri Biswas
- Department of Chemistry, Indian Institute of Technology Hyderabad, Sangareddy-502285, Telangana, India.
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