Dynamics of Ionic Liquid through Intrinsic Vibrational Probes Using the Dispersion-Corrected DFT Functionals

Biswas, Aritri and Mallik, Bhabani S. (2021) Dynamics of Ionic Liquid through Intrinsic Vibrational Probes Using the Dispersion-Corrected DFT Functionals. Journal of Physical Chemistry B, 125 (25). pp. 6994-7008. ISSN 15206106

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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. © 2021 American Chemical Society.

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IITH Creators:
IITH CreatorsORCiD
Mallik, Bhabani Shankarhttp://orcid.org/0000-0001-9657-1497
Item Type: Article
Additional Information: Publisher: American Chemical Society
Uncontrolled Keywords: Autocorrelation functions; Exchange-correlation functionals; First principles molecular dynamics; Frequency distributions; Hydrogen bonding interactions; Perdew-burke-ernzerhof; Spectroscopic signatures; Structural interactions
Subjects: Chemistry
Divisions: Department of Chemistry
Depositing User: Mrs Haseena VKKM
Date Deposited: 30 May 2022 09:31
Last Modified: 30 May 2022 09:31
URI: http://raiith.iith.ac.in/id/eprint/9276
Publisher URL: https://doi.org/10.1021/acs.jpcb.1c04960
OA policy: https://v2.sherpa.ac.uk/id/publication/21299
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