An ab initio anharmonic approach to study vibrational spectra of small ammonia clusters

Ho, Kun-Lin; Lee, Lo-Yun; Katada, Marusu; Fujii, Asuka; Kuo, Jer‐Lai

doi:10.1039/c6cp05537k

Cited by 32 publications

(27 citation statements)

References 33 publications

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“…In the last decade, there have been many theoretical analyses of the FR of O‐H and C‐H vibrations [6–11] based on anharmonic terms of the potential energy surface (PES) and the coupling strength of the FR is found to be typically in the order of 30 to 40 cm −1 . Recently, there are also a few works using ab initio methods to access the anharmonic vibrational coupling behind vibrational spectra of clusters of ammonia, amine, and anilines, and the similar coupling strength is reported [12–14] …”

Section: Introductionmentioning

confidence: 69%

Strong Fermi Resonance Associated with Proton Motions Revealed by Vibrational Spectra of Asymmetric Proton‐Bound Dimers

Huang

Shishido

Lin

et al. 2020

Angew. Chem. Int. Ed.

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Infrared spectra for as eries of asymmetric protonbound dimers with protonated trimethylamine (TMA-H +)a s the proton donor were recorded and analyzed.T he frequency of the N-H + stretching mode is expected to red shift as the proton affinity of proton acceptors increases.T he observed band, however,s hows ap eculiar splitting of approximately 300 cm À1 with the intensity shifting pattern resembling at wolevel system. Theoretical investigation reveals that the observed band splitting and its extraordinarily large gap of around 300 cm À1 is aresult of strong coupling between the fundamental of the proton stretching mode and overtone states of the two proton bending modes,t hat is commonly knowna sF ermi resonance (FR). We also provide ageneral theoretical model to link the strong FR coupling to the quasi-two-level system. Since the model does not depend on the molecular specification of TMA-H + ,t he strong coupling we observed is an intrinsic property associated with proton motions.

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Section: Introductionmentioning

confidence: 69%

Strong Fermi Resonance Associated with Proton Motions Revealed by Vibrational Spectra of Asymmetric Proton‐Bound Dimers

Huang

Shishido

Lin

et al. 2020

Angew. Chem. Int. Ed.

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“…8 The hydrogen bond of the ammonia dimer is considerably bent from the ideal linear configuration (unlike that of the water dimer), 9 which has led to extensive studies of this particular intermolecular interaction. [8][9][10][11][12][13][14][15][16][17][18][19] It is now evident from both experimental and theoretical studies that the intermolecular PES of the ammonia dimer is indeed extremely flat. [16][17][18] To disentangle the contributions of vibrational motions on the PES, one needs to achieve well-resolved vibrational spectra.…”

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confidence: 99%

Deconstructing Vibrational Motions on the Potential Energy Surfaces of Hydrogen-Bonded Complexes

et al. 2021

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Internal vibrations underlie transient structure formation, spectroscopy, and dynamics. However, at least two challenges exist when aiming to elucidate the contributions of vibrational motions on the potential energy surfaces. One is the acquisition of well-resolved experimental infrared spectra, and the other is the development of efficient theoretical methodologies that reliably predict band positions, relative intensities, and substructures. Here, we report size-specific infrared spectra of ammonia clusters to address these two challenges. Unprecedented agreement between experiment and state-of-the-art quantum simulations reveals that the vibrational spectra are mainly contributed by proton-donor ammonia. A striking Fermi resonance observed at approximately 3210 and 3250 cm −1 originates from the coupling of NH symmetric stretch fundamentals with overtones of free and hydrogen-bonded NH bending, respectively. These novel, intriguing findings contribute to a better understanding of vibrational motions in a large variety of hydrogen-bonded complexes with orders of magnitude improvements in spectral resolution, efficiency, and specificity.

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“…Moreover, the structures of the nitrous oxide clusters are also stabilized by dipole–dipole interactions. However, we found that acetonitrile clusters exhibits completely different structural arrangements as compared to neutral water clusters 20‐22,29,61‐64 and neutral ammonia clusters 35,65‐67 …”

Section: Resultsmentioning

confidence: 83%

Binding energies and isomer distribution of neutral acetonitrile clusters

Malloum

Fifen

Conradie

2020

Int J of Quantum Chemistry

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Structures and relative stabilities of neutral acetonitrile clusters up to decamer have been investigated. We used the ABCluster code to thoroughly explore the potential energy surfaces (PESs) of the acetonitrile clusters and to generate initial geometries, which are further fully optimized at the MN15/6-31++G(d,p) level of theory. Our exploration yielded several new local and global minima structures of the acetonitrile clusters. We located new global minimum structures of the acetonitrile pentamer to decamer. The results show that the PESs of the acetonitrile clusters are very flat, yielding several isoenergetic structures. Our investigations also revealed that the stability of the acetonitrile clusters is due both to CHÁ Á ÁN and dipole-dipole interactions. Structures stabilized by the latter are found to be more stable than those stabilized by the former at low temperatures. Furthermore, we examined the effect of temperature on the stability of the structures of the acetonitrile clusters for temperatures in the range 20 to 400 K. We found that several structures contribute to the population of the clusters at high temperatures, and also that a significant contribution to the population comes from isomers that lie within 2.0 kcal/mol from the most stable one. In addition, we used the most stable structures to compute the binding energies of the acetonitrile clusters and to assess the performance of some DFT functionals (MN15, ωB97XD, PW6B95D3, and B2PLYP) in comparison with the MP2 method associated to the aug-cc-pVTZ basis set in calculating the binding energies. We found that the MN15 functional performs better than ωB97XD and PW6B95D3, and that MN15 is less sensitive to the basis set change. We also used an extrapolation scheme to calculate the binding energies of the acetonitrile clusters at the highly accurate W1BD, CBS-QB3, and G4MP2 levels of theory. The resulting binding energies are recommended for future benchmarking of the acetonitrile clusters. K E Y W O R D S acetonitrile clusters, binding energy, DFT functionals, molecular clusters, relative energy, temperature effects, ABCluster code

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An ab initio anharmonic approach to study vibrational spectra of small ammonia clusters

Cited by 32 publications

References 33 publications

Strong Fermi Resonance Associated with Proton Motions Revealed by Vibrational Spectra of Asymmetric Proton‐Bound Dimers

Strong Fermi Resonance Associated with Proton Motions Revealed by Vibrational Spectra of Asymmetric Proton‐Bound Dimers

Deconstructing Vibrational Motions on the Potential Energy Surfaces of Hydrogen-Bonded Complexes

Binding energies and isomer distribution of neutral acetonitrile clusters

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