The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Hajime Torii - One of the best experts on this subject based on the ideXlab platform.
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Pressure dependence of the Liquid structure and the Raman noncoincidence effect of Liquid Methanol revisited
Pure and Applied Chemistry, 2004Co-Authors: Hajime ToriiAbstract:Pressure dependence of the Liquid structure and the Raman noncoincidence effect of Liquid Methanol is examined with the combination of molecular dynamics (MD) simula- tions and the intermolecular resonant vibrational interactions determined by the transition di- pole coupling (TDC) mechanism (MD/TDC method). It is shown that the observed decrease of the Raman noncoincidence ν NCE of the CO stretching band with increasing density re- ported in the literature is quantitatively reproduced by the present calculation. As the density increases, the hydrogen bonds get slightly shorter, but molecules belonging to different hy- drogen-bond chains get closer to each other to a greater extent. This anisotropic change in the Liquid structure is the reason for the behavior of ν NCE . It is also shown that the concen- tration dependence of ν NCE in the Methanol/CCl 4 binary mixtures reported in a previous study, and the pressure dependence of ν NCE in Methanol may be described in a consistent way as a function of the number density of Methanol in the Liquid systems.
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Liquid structures and the infrared and isotropic anisotropic raman noncoincidence in Liquid Methanol a Methanol licl solution and a solvated electron in Methanol molecular dynamics and ab initio molecular orbital studies
Journal of Physical Chemistry A, 1999Co-Authors: Hajime ToriiAbstract:The relationship between the Liquid structures, vibrational interactions, and the wavenumber differences among the infrared (IR), isotropic Raman, and anisotropic Raman components of vibrational bands (the noncoincidence effect) is analyzed theoretically for the OH stretching bands of neat Liquid Methanol and a Methanol−LiCl solution. The analysis is also carried out for the CO stretching band of neat Liquid Methanol for comparison. The IR and Raman spectra are calculated on the basis of the transition dipole coupling (TDC) mechanism and the Liquid structures derived from molecular dynamics (MD) simulations (the MD/TDC method). It is shown that the signs and magnitudes of the noncoincidence effect observed for the OH and CO stretching bands of Liquid Methanol, which are significantly different between these two bands, are well reproduced by the calculations based on the same set of Liquid structures and the same mechanism of vibrational interactions. The analysis of the origin of the noncoincidence effect...
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Liquid Structures and the Infrared and Isotropic/Anisotropic Raman Noncoincidence in Liquid Methanol, a Methanol−LiCl Solution, and a Solvated Electron in Methanol: Molecular Dynamics and ab Initio Molecular Orbital Studies
The Journal of Physical Chemistry A, 1999Co-Authors: Hajime ToriiAbstract:The relationship between the Liquid structures, vibrational interactions, and the wavenumber differences among the infrared (IR), isotropic Raman, and anisotropic Raman components of vibrational bands (the noncoincidence effect) is analyzed theoretically for the OH stretching bands of neat Liquid Methanol and a Methanol−LiCl solution. The analysis is also carried out for the CO stretching band of neat Liquid Methanol for comparison. The IR and Raman spectra are calculated on the basis of the transition dipole coupling (TDC) mechanism and the Liquid structures derived from molecular dynamics (MD) simulations (the MD/TDC method). It is shown that the signs and magnitudes of the noncoincidence effect observed for the OH and CO stretching bands of Liquid Methanol, which are significantly different between these two bands, are well reproduced by the calculations based on the same set of Liquid structures and the same mechanism of vibrational interactions. The analysis of the origin of the noncoincidence effect...
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Local order and transition dipole coupling in Liquid Methanol and acetone as the origin of the Raman noncoincidence effect
The Journal of Chemical Physics, 1993Co-Authors: Hajime Torii, Mitsuo TasumiAbstract:Model calculations are performed on the Raman noncoincidence effect (frequency difference between the isotropic and anisotropic components) observed for the C–O stretching band of Liquid Methanol and the C=O stretching band of Liquid acetone. Microscopic Liquid structures are obtained by Monte Carlo simulations, and coupling between molecular vibrations is introduced by the transition dipole coupling mechanism. Ab initio molecular orbital calculations are also performed to check the validity of the assumed direction of the transition dipole for the C–O stretching mode of Methanol. The different signs of the Raman noncoincidence between the C–O stretching band of Liquid Methanol and the C=O stretching band of Liquid acetone can be explained by the transition dipole coupling mechanism. The calculated magnitudes of the frequency separations between the isotropic and anisotropic components are in good agreement with the experimental results. Pressure dependence of the Raman noncoincidence is also calculated and compared with the experimental results. In the case of the C–O stretching band of Liquid Methanol, local anisotropy in the pressure‐induced changes of the Liquid structure is shown to be important for the pressure dependence of the Raman noncoincidence.
Vincenzo Schettino - One of the best experts on this subject based on the ideXlab platform.
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The solvation dynamics of Na+ and K+ ions in Liquid Methanol
Theoretical Chemistry Accounts, 2007Co-Authors: Cristian Faralli, Marco Pagliai, Gianni Cardini, Vincenzo SchettinoAbstract:The structure of the solvation shell of Na+ and K+ in fully deuterated Liquid Methanol has been studied by ab initio Car-Parrinello molecular dynamics simulations. The solvent cage has been found relatively stable and this property has been explained by means of charge transfer and electrostatic interactions as was previously done for Li+ in the same solvent. The differences with Li+ such as the increase of the coordination number going from Li+ to K+ and the reduced stability of the cage have been ascribed to the increase in the ionic radius.
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Structure and dynamics of Br- ion in Liquid Methanol.
The journal of physical chemistry. B, 2006Co-Authors: Cristian Faralli, Marco Pagliai, Gianni Cardini, Vincenzo SchettinoAbstract:A Car−Parrinello molecular dynamics simulation has been performed on a solution of Br- in Liquid Methanol analyzing with particular attention charge transfer and polarization effects. The first solvation shell has been characterized in terms of H-bonds, and it has been found that the high polarization of the bromide gives rise to a stable solvent cage. The differences in the coordination number with the chloride can be ascribed to the ionic radius and to the stronger perturbations brought by the solvent to the bromide ion.
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Solvation dynamics of Li+ and Cl- ions in Liquid Methanol.
The journal of physical chemistry. B, 2005Co-Authors: Marco Pagliai, Gianni Cardini, Vincenzo SchettinoAbstract:Car−Parrinello molecular dynamics simulations have been performed on Li+ and Cl- in fully deuterated Liquid Methanol. The results have been compared with available experimental and theoretical data. It has been found that the lithium cation has a stable tetrahedral coordination, whereas the chloride anion presents an average coordination number of 3.56. The polarization effects induced by the ion on the solvent have been analyzed in terms of Wannier function centers. Particular attention has been devoted to the charge transfer, which is particularly important in these types of systems. Evidence for the stability of the lithium cation solvent cage also has been found in the vibrational spectra.
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Hydrogen bond dynamics in Liquid Methanol
The Journal of Chemical Physics, 2003Co-Authors: Marco Pagliai, Gianni Cardini, Roberto Righini, Vincenzo SchettinoAbstract:A Car–Parrinello molecular dynamics simulation has been performed on fully deuterated Liquid Methanol. The results are compared with the latest available experimental and theoretical data. It is shown that the Liquid is aggregated in chains of hydrogen bonded molecules. The structure of the aggregates is characterized and it is found that the dynamics includes a fast and a slow regime. The weak H bond formed by the methyl group hydrogens and oxygen atom of surrounding molecules has been characterized. The importance of inductive effects is shown and discussed in terms of maximally localized Wannier function centers. Special attention is devoted to clarify how the molecular dipole moment depends on the number of H bonds formed by each molecule. The IR spectrum is computed and analyzed in terms of H-bond interactions. Insights on the short time dynamics and on the H-bond network are illustrated.
Valentín G. Baonza - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic properties of compressed Liquid Methanol in the vicinity of the freezing line
Journal of Chemical & Engineering Data, 2007Co-Authors: Mercedes Taravillo, Mercedes Cáceres, Javier Núñez, Francisco J. Pérez, Valentín G. BaonzaAbstract:We present direct measurements of the isothermal compressibility (κT) and thermal expansion coefficient (αp) of Liquid Methanol using an expansion technique. The measurements of κT were carried out along six isotherms from (208.17 to 298.16) K at pressures up to 101 MPa. For αp, we have measured four isobars from (0.59 to 80.03) MPa from 195 K up to 300 K. Our experimental results of αp(T) for the 0.59 MPa isobar exhibit a minimum around 224 K. A clear shift of the minimum to higher temperatures is observed as the pressure increases along the different isobars. Interestingly, the minima for the isobars of αp(ρ) take place within a narrow range of densities, around 26.5 mol·dm-3 (about 3.15 times the critical density).
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Pressure tuning of the Fermi resonance in Liquid Methanol: implications for the analysis of high-pressure vibrational spectroscopy experiments.
The Journal of chemical physics, 2005Co-Authors: Ariel Arencibia, Mercedes Taravillo, Mercedes Cáceres, Javier Núñez, Valentín G. BaonzaAbstract:It has been argued that pressure tuning allows for unambiguous assignment of the nonperturbed bands involved in the Fermi coupling of molecular systems in the condensed phase. Here we study the pressure evolution of the Fermi resonance occurring in Liquid Methanol between the symmetric methyl-stretch fundamental and the methyl-bending overtones. Our analysis is based on Raman experiments in both stretching and bending fundamental regions, which are used to evaluate the effect of pressure on accidental degeneracies occurring in the vibrational spectra of Liquid Methanol. We emphasize that the difference in frequency of the Fermi doublet constitutes the governing quantity to determine the condition at which the exact degeneracy of the unperturbed modes occurs. Analysis based on the intensity ratio of the Fermi doublet must be disregarded. We confirm the necessity of measuring the full vibrational spectrum under pressure in order to obtain the Fermi coupling parameters unambiguously and to give a correct ass...
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Effect of Pressure on Hydrogen Bonding in Liquid Methanol
Physical Review Letters, 2002Co-Authors: Ariel Arencibia, Mercedes Taravillo, F. J. Pérez, Valentín G. BaonzaAbstract:We have investigated the effect of pressure on the hydrogen bonding in Liquid Methanol using Raman spectroscopy. Specifically, we have measured the OH and CO stretching modes and assigned the bands, in agreement with recent IR and crossed molecular beam experiments on Methanol clusters. At about 7 to 8 kbar, we note indications that the intrinsic nature of the Methanol clusters in our samples has changed. Our results provide support for and extend conclusions derived from Monte Carlo simulations, explain anomalies observed by previous researchers, and provide new insights into general hydrogen-bonding phenomena.
Yi Luo - One of the best experts on this subject based on the ideXlab platform.
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The microscopic structure of Liquid Methanol from Raman spectroscopy.
The journal of physical chemistry. B, 2010Co-Authors: Ke Lin, Xiaoguo Zhou, Yi Luo, Shilin LiuAbstract:The microscopic structure of Liquid Methanol has been systematically investigated with Raman spectroscopy in a temperature range of 15−55 °C. The unbonded free −OH stretching vibrational band has been observed at ∼3660 cm−1 in pure Liquid. With the aid of depolarization measurements and theoretical calculations, four featured spectral components have been unambiguously identified and assigned to four well-defined vibrational modes of clusters in chain or ring forms. Furthermore, the cluster size distribution and its temperature dependence have been derived from the spectral fittings for the first time, which lead to the conclusion that the trimer, tetramer, and pentamer are the dominant clusters in Liquid Methanol, taking up more than 50% of total clusters.
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Chemical and electronic structures of Liquid Methanol from x-ray emission spectroscopy and density functional theory
Physical Review B, 2005Co-Authors: Stepan Kashtanov, Andreas Augustson, Jan-erik Rubensson, Joseph Nordgren, Hans Ågren, Jinghua Guo, Yi LuoAbstract:Chemical and electronic structures of Liquid Methanol from x-ray emission spectroscopy and density functional theory
Lars G. M. Pettersson - One of the best experts on this subject based on the ideXlab platform.
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Core-hole-induced dynamical effects in the x-ray emission spectrum of Liquid Methanol
The Journal of chemical physics, 2017Co-Authors: Mathias P. Ljungberg, Iurii Zhovtobriukh, Osamu Takahashi, Lars G. M. PetterssonAbstract:We compute the x-ray emission spectrum of Liquid Methanol, with the dynamical effects that result from the creation of the core hole included in a semiclassical way. Our method closely reproduces a fully quantum mechanical description of the dynamical effects for relevant one-dimensional models of the hydrogen-bonded Methanol molecules. For the Liquid, we find excellent agreement with the experimental spectrum, including the large isotope effect in the first split peak. The dynamical effects depend sensitively on the initial structure in terms of the local hydrogen-bonding (H-bonding) character: non-donor molecules contribute mainly to the high-energy peak while molecules with a strong donating H-bond contribute to the peak at lower energy. The spectrum thus reflects the initial structure mediated by the dynamical effects that are, however, seen to be crucial in order to reproduce the intensity distribution of the recently measured spectrum.
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core hole induced dynamical effects in the x ray emission spectrum of Liquid Methanol
arXiv: Materials Science, 2017Co-Authors: Mathias P. Ljungberg, Iurii Zhovtobriukh, Osamu Takahashi, Lars G. M. PetterssonAbstract:We compute the x-ray emission spectrum (XES) of Liquid Methanol, with the dynamical effects that result from the creation of the core hole included in a semiclassical way. Our method closely reproduces a fully quantum mechanical description of the dynamical effects for relevant one-dimensional models of the hydrogen-bonded Methanol molecules. For the Liquid we find excellent agreement with the experimental spectrum, including the large isotope effect in the first split peak. The dynamical effects depend sensitively on the initial structure in terms of the local hydrogen-bonding (H-bonding) character; non-donor molecules contribute mainly to the high-energy peak while molecules with a strong donated H-bond contribute to the peak at lower energy. The spectrum thus reflects the initial structure mediated by the dynamical effects that are, however, seen to be crucial in order to reproduce the intensity distribution of the recently measured spectrum.