Characteristics of Low-Frequency Molecular Phonon Modes Studied by THz Spectroscopy and Solid-State ab Initio Theory: Polymorphs I and III of Diflunisal

Zhang, Feng; Wang, Houng-Wei; Tominaga, Kazuhiro; Hayashi, M.

doi:10.1021/acs.jpcb.5b08798

Cited by 32 publications

(22 citation statements)

References 57 publications

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“…It has been common to vary their values so as to minimize the deviation between the calculated and experimental crystal structures. In some cases this is achieved by minimizing the error in the calculated volume [43,44], in others the distortion of the cell is minimized [45].…”

Section: Methodsmentioning

confidence: 99%

Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Kendrick

Burnett

2019

J Infrared Milli Terahz Waves

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A number of DFT programs with various combinations of pseudo-potentials and van der Waals' dispersive corrections have been used to optimize the structure of sodium peroxodisulfate, Na 2 (SO 4) 2 , and to calculate the infrared, attenuated total reflectance and terahertz absorption spectra of the powdered crystal. Comparison of the results from the different methods highlights the problems of calculating the absorption spectrum reliably. In particular the low frequency phonon modes are especially sensitive to the choice of grids to represent the wavefunction or the charge distribution, k-point integration grid and the energy cutoff. A comparison is made between the Maxwell-Garnett (MG) and Bruggeman effective medium methods used to account for the effect of crystal shape on the predicted spectrum. Possible scattering of light by air inclusions in the sample and by larger particles of Na 2 (SO 4) 2 is also considered using the Mie method. The results of the calculations are compared with experimental measurements of the transmission and attenuated total reflection spectra.

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Section: Methodsmentioning

confidence: 99%

Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Kendrick

Burnett

2019

J Infrared Milli Terahz Waves

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“…Conversely, vibrational modes at higher frequencies (far-IR) are rather straightforward to calculate, because the contribution of intramolecular motion becomes dominant [23,24]. Some of the bands can be simulated by considering a small number of atoms.…”

Section: Resultsmentioning

confidence: 99%

Terahertz Spectroscopy for Characterization of Hydrogen Bonding and Cross-linked Structure Dynamics in Polyurethane

Hoshina

Saito

Furuhashi

et al. 2020

J Infrared Milli Terahz Waves

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Terahertz (THz) absorption spectra of cross-linked polyurethane films were observed at 30-180°C. The obtained spectra displayed characteristic absorption bands. A band observed at 2.6 THz was assigned to the C=O•••N-H hydrogen bond vibration using previously reported data. DFT calculation results confirmed that a band at 7.5 THz arises owing to the torsional vibration of cross-linked molecules containing urethane bonds. The slight changes in the temperature-dependent spectra were analyzed by the first derivative of absorption intensity with temperature. The thermal behavior of absorption intensities indicates the dynamics of hydrogen bonds and cross-linked structures in polyurethane films.

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“…For molecular vibrations in crystalline solids, a striking difference from gas‐phase vibrations is that they have well‐defined intermolecular vibrational coordinates. The intermolecular and intramolecular vibrations in most cases mix together in the low‐frequency normal modes ,. Concerning a certain THz mode, unless the contributions from the intermolecular and intramolecular vibrations to the vibrational energy are quantified, the understanding of its nature is incomplete.…”

Section: Resultsmentioning

confidence: 99%

Application of THz Vibrational Spectroscopy to Molecular Characterization and the Theoretical Fundamentals: An Illustration Using Saccharide Molecules

Zhang

Wang

Tominaga

et al. 2017

Chemistry An Asian Journal

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This work illustrates several theoretical fundamentals for the application of THz vibrational spectroscopy to molecular characterization in the solid state using two different types of saccharide systems as examples. Four subjects have been specifically addressed: (1) the qualitative differences in the molecular vibrational signatures monitored by THz and mid-IR vibrational spectroscopy; (2) the selection rules for THz vibrational spectroscopy as applied to crystalline and amorphous systems; (3) a normal mode simulation, using α-l-xylose as an example; and (4) a rigorous mode analysis to quantify the percentage contributions of the intermolecular and intramolecular vibrations to the normal mode of interest.

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Characteristics of Low-Frequency Molecular Phonon Modes Studied by THz Spectroscopy and Solid-State ab Initio Theory: Polymorphs I and III of Diflunisal

Cited by 32 publications

References 57 publications

Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate

Terahertz Spectroscopy for Characterization of Hydrogen Bonding and Cross-linked Structure Dynamics in Polyurethane

Application of THz Vibrational Spectroscopy to Molecular Characterization and the Theoretical Fundamentals: An Illustration Using Saccharide Molecules

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