Advances in Anharmonic Methods and Their Applications to Vibrational Spectroscopies

Beć, Krzysztof B.; Grabska, Justyna; Ozaki, Yukihiro

doi:10.1007/978-981-10-5651-2_20

Cited by 14 publications

(13 citation statements)

References 76 publications

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“…Numerous overlapping bands populate NIR spectra of even relatively simple molecules [16,31]. This makes their detailed analysis difficult, and the interpretation of the leading contributions is not as straightforward as it is for the corresponding IR spectra.…”

Section: Resultsmentioning

confidence: 99%

“…Coincidently, quantum chemistry offers affordable methods (harmonic approximation) for the adequately accurate simulation of IR and Raman spectra [29,30]. In contrast, prediction of NIR bands require resource intensive anharmonic methods [31,32]. The difference in resource demand (harmonic vs. anharmonic approximation) is significant, and theoretical NIR studies of complex molecules have only recently appeared [33,34,35,36,37,38].…”

Section: Introductionmentioning

confidence: 99%

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Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

et al. 2019

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Melamine (IUPAC: 1,3,5-Triazine-2,4,6-triamine) attracts high attention in analytical vibrational spectroscopy due to its misuse as a food adulterant. Vibrational spectroscopy [infrared (IR) and Raman and near-infrared (NIR) spectroscopy] is a major quality control tool in the detection and quantification of melamine content. The physical background for the measured spectra is not interpreted in analytical spectroscopy using chemometrics. In contrast, quantum mechanical calculations are capable of providing deep and independent insights therein. So far, the NIR region of crystalline melamine has not been studied by quantum mechanical calculations, while the investigations of its IR spectra have remained limited. In the present work, we employed fully anharmonic calculation of the NIR spectrum of melamine based on finite models, and also performed IR spectral simulation by using an infinite crystal model—periodic in three dimensions. This yielded detailed and unambiguous NIR band assignments and revised the previously known IR band assignments. We found that the out-of-plane fundamental transitions, which are essential in the IR region, are markedly more sensitive to out-of-plane inter-molecular interactions of melamine than NIR transitions. Proper description of the chemical surrounding of the molecule of melamine is more important than the anharmonicity of its vibrations. In contrast, the NIR bands mostly arise from in-plane vibrations, and remain surprisingly insensitive to the chemical environment. These findings explain previous observations that were reported in IR and NIR analytical studies of melamine.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

et al. 2019

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“…Investigations into the solution phase often find a useful addition of computationally affordable implicit solvation model. Several different approaches may be found in recent literature, e.g., Polarizable Continuum Model (PCM) and derivatives; conductor-like polarizable continuum model (CPCM) or integral equation formalism variant (IEF-PCM); these approximate description of solvation allow for efficient increase in the quality of simulations performed in solution phase (Beć et al, 2016a, 2017).…”

Section: Theoretical Near-infrared Spectroscopy–an Overview Of the Emmentioning

confidence: 99%

“…Generally applicable anharmonic computational schemes, e.g., VPT2 or VSCF, through simplifications are affordable enough to be used for the calculation of a large number of transitions, e.g., first overtones and binary combinations of all modes (Beć et al, 2017). The general methods are highly useful in the simulation of an entire NIR spectra as overlapping of the manifold bands in this region would make it extremely difficult to rely on any arbitrary selection of particular modes.…”

Section: Theoretical Near-infrared Spectroscopy–an Overview Of the Emmentioning

confidence: 99%

“…These methods acquire their efficiency by approximating the anharmonic potential on a possibly lowest number of energy evaluations. Thus, effectively they “capture” a limited amount of anharmonicity, which may be enough in most cases, but not necessarily, e.g., when the mode deviates from the harmonic oscillator to a certain degree (Beć et al, 2017). Several attempts to improve accuracy have been made e.g., by transformation of the vibrational coordinates; this remains an active field of research (Yagi et al, 2012; Thomsen et al, 2014).…”

Section: Theoretical Near-infrared Spectroscopy–an Overview Of the Emmentioning

confidence: 99%

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Breakthrough Potential in Near-Infrared Spectroscopy: Spectra Simulation. A Review of Recent Developments

2019

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Near-infrared (12,500–4,000 cm −1 ; 800–2,500 nm) spectroscopy is the hallmark for one of the most rapidly advancing analytical techniques over the last few decades. Although it is mainly recognized as an analytical tool, near-infrared spectroscopy has also contributed significantly to physical chemistry, e.g., by delivering invaluable data on the anharmonic nature of molecular vibrations or peculiarities of intermolecular interactions. In all these contexts, a major barrier in the form of an intrinsic complexity of near-infrared spectra has been encountered. A large number of overlapping vibrational contributions influenced by anharmonic effects create complex patterns of spectral dependencies, in many cases hindering our comprehension of near-infrared spectra. Quantum mechanical calculations commonly serve as a major support to infrared and Raman studies; conversely, near-infrared spectroscopy has long been hindered in this regard due to practical limitations. Advances in anharmonic theories in hyphenation with ever-growing computer technology have enabled feasible theoretical near-infrared spectroscopy in recent times. Accordingly, a growing number of quantum mechanical investigations aimed at near-infrared region has been witnessed. The present review article summarizes these most recent accomplishments in the emerging field. Applications of generalized approaches, such as vibrational self-consistent field and vibrational second order perturbation theories as well as their derivatives, and dense grid-based studies of vibrational potential, are overviewed. Basic and applied studies are discussed, with special attention paid to the ones which aim at improving analytical spectroscopy. A remarkable potential arises from the growing applicability of anharmonic computations to solving the problems which arise in both basic and analytical near-infrared spectroscopy. This review highlights an increased value of quantum mechanical calculations to near-infrared spectroscopy in relation to other kinds of vibrational spectroscopy.

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The New Avenue – Theoretical Simulation of NIR Spectra and its Potential in Analytical Applications

Beć

Grabska

Huck

2022

Sense the Real Change: Proceedings of the 20th International Conference on Near Infrared Spectroscopy

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Advances in Anharmonic Methods and Their Applications to Vibrational Spectroscopies

Cited by 14 publications

References 76 publications

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

Distinct Difference in Sensitivity of NIR vs. IR Bands of Melamine to Inter-Molecular Interactions with Impact on Analytical Spectroscopy Explained by Anharmonic Quantum Mechanical Study

Breakthrough Potential in Near-Infrared Spectroscopy: Spectra Simulation. A Review of Recent Developments

The New Avenue – Theoretical Simulation of NIR Spectra and its Potential in Analytical Applications

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