Invited Review: Modern Methods for Accurately Simulating the Terahertz Spectra of Solids

Ruggiero, Michael T.

doi:10.1007/s10762-019-00648-3

Cited by 47 publications

(31 citation statements)

References 216 publications

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“…It is currently being intensively studied [29,65,66], since various intermolecular vibrations can be observed in it, in particular, because of the presence of intermolecular H-bonds [36,[67][68][69]. The double harmonic approximation provides a reasonable description of the IR/Raman spectra of organic crystals in the low-frequency spectral range [29,30,70,71].…”

Section: Ir Spectrum In the Low-frequency Regionmentioning

confidence: 99%

Combined X-ray Crystallographic, IR/Raman Spectroscopic, and Periodic DFT Investigations of New Multicomponent Crystalline Forms of Anthelmintic Drugs: A Case Study of Carbendazim Maleate

et al. 2020

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Synthesis of multicomponent solid forms is an important method of modifying and fine-tuning the most critical physicochemical properties of drug compounds. The design of new multicomponent pharmaceutical materials requires reliable information about the supramolecular arrangement of molecules and detailed description of the intermolecular interactions in the crystal structure. It implies the use of a combination of different experimental and theoretical investigation methods. Organic salts present new challenges for those who develop theoretical approaches describing the structure, spectral properties, and lattice energy Elatt. These crystals consist of closed-shell organic ions interacting through relatively strong hydrogen bonds, which leads to Elatt > 200 kJ/mol. Some technical problems that a user of periodic (solid-state) density functional theory (DFT) programs encounters when calculating the properties of these crystals still remain unsolved, for example, the influence of cell parameter optimization on the Elatt value, wave numbers, relative intensity of Raman-active vibrations in the low-frequency region, etc. In this work, various properties of a new two-component carbendazim maleate crystal were experimentally investigated, and the applicability of different DFT functionals and empirical Grimme corrections to the description of the obtained structural and spectroscopic properties was tested. Based on this, practical recommendations were developed for further theoretical studies of multicomponent organic pharmaceutical crystals.

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Section: Ir Spectrum In the Low-frequency Regionmentioning

confidence: 99%

Combined X-ray Crystallographic, IR/Raman Spectroscopic, and Periodic DFT Investigations of New Multicomponent Crystalline Forms of Anthelmintic Drugs: A Case Study of Carbendazim Maleate

et al. 2020

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“…Several review papers on THz sensing exist in the literature, such as [17]- [20]. Up to the authors' knowledge, however, this paper is the first article that presents a holistic overview of signal processing and machine learning techniques for efficient THz sensing.…”

Section: E Contributions Of This Workmentioning

confidence: 99%

Signal Processing and Machine Learning Techniques for Terahertz Sensing: An Overview

Helal¹,

Sarieddeen²,

Dahrouj³

et al. 2021

Preprint

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Following the recent progress in Terahertz (THz) signal generation and radiation methods, joint THz communications and sensing applications are shaping the future of wireless systems. Towards this end, THz spectroscopy is expected to be carried over user equipment devices to identify material and gaseous components of interest. THz-specific signal processing techniques should complement this re-surged interest in THz sensing for efficient utilization of the THz band. In this paper, we present an overview of these techniques, with an emphasis on signal pre-processing (standard normal variate normalization, min-max normalization, and Savitzky-Golay filtering), feature extraction (principal component analysis, partial least squares, t-distributed stochastic neighbor embedding, and nonnegative matrix factorization), and classification techniques (support vector machines, k-nearest neighbor, discriminant analysis, and naive Bayes). We also address the effectiveness of deep learning techniques by exploring their promising sensing capabilities at the THz band. Lastly, we investigate the performance and complexity trade-offs of the studied methods in the context of joint communications and sensing; we motivate the corresponding usecases, and we present few future research directions in the field.

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“…The terahertz spectrum is composed of a mixture of hydrogens, weak covalent bonds, ionic bonds and van der Waals force in the solid states [ 30 ]. These complex and highly entangled molecular interactions make the terahertz spectrum results difficult to explain, so it needs relatively complex calculation and simulation [ 31 ]. Density functional theory (DFT), as a very useful means of quantum mechanics calculation, is able to explain and assign in detail the complex molecular motions obtained from THz experiments and understand the basic origin of material properties [ 32 ].…”

Section: Introductionmentioning

confidence: 99%

Terahertz and Raman Spectroscopic Investigation of Monohydrate Cocrystal of Antitubercular Isoniazid with Protocatechuic Acid

Fang

Zhang

et al. 2021

Pharmaceutics

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Pharmaceutical cocrystal provides an alternative modification strategy for the formulation development of drugs owning to their potential ability to improve the physicochemical properties of active pharmaceutical ingredients (APIs) efficiently by changing inter-molecular interactions between raw materials. Isoniazid (INH) is an indispensable main drug for the treatment of tuberculosis, but its tablet formulation is unstable and prone to degradation. In the present study, the monohydrate cocrystal of INH and protocatechuic acid (PA) was prepared by solvent evaporation using PA as cocrystal former to optimize the properties of INH. The parent materials and corresponding 1:1 molar ratio INH-PA monohydrate cocrystal have been characterized by the terahertz time-domain (THz-TDS) and Raman spectroscopy. The THz absorption spectra displayed that there were obvious differences between the peaks of experimental cocrystal and the parent materials, and the same situation was found in Raman vibrational spectra. In addition, density functional theory (DFT) was applied to simulating and optimizing the structure of INH-PA monohydrate cocrystal and supplied corresponding vibrational modes. Our results provided a unique method to characterize the formation of INH-PA monohydrate cocrystal at the molecular-level and a lot of information about cocrystal structure and intra-molecular and/or inter-molecular hydrogen bond interactions in the emerging pharmaceutical cocrystal fields.

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Invited Review: Modern Methods for Accurately Simulating the Terahertz Spectra of Solids

Cited by 47 publications

References 216 publications

Combined X-ray Crystallographic, IR/Raman Spectroscopic, and Periodic DFT Investigations of New Multicomponent Crystalline Forms of Anthelmintic Drugs: A Case Study of Carbendazim Maleate

Combined X-ray Crystallographic, IR/Raman Spectroscopic, and Periodic DFT Investigations of New Multicomponent Crystalline Forms of Anthelmintic Drugs: A Case Study of Carbendazim Maleate

Signal Processing and Machine Learning Techniques for Terahertz Sensing: An Overview

Terahertz and Raman Spectroscopic Investigation of Monohydrate Cocrystal of Antitubercular Isoniazid with Protocatechuic Acid

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