Low-frequency Raman spectra of sub- and supercritical CO2: Qualitative analysis of the diffusion coefficient behavior

Idriss, Hicham; Longelin, S.; Damay, P.; Leclercq, F.

doi:10.1063/1.1992476

Cited by 4 publications

(1 citation statement)

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“…Molecular dynamics simulations of the CO 2 fluid have been performed at eight different temperatures, i.e., at 250, 270, 285, 298, and 303 K (along the liquid−gas CC) and at 306, 313, and 320 K (along the CI) in the isothermal−isobaric ( N , p , T ) ensemble. As pointed out in our previous works, , the disadvantages of using the molecular dynamics simulation to study supercritical fluids (particularly near the critical point) is related to the box size (which limits the correlation length explored) and to the knowledge of the critical point associated with the intermolecular potential model used in the simulation (the determination of which is not trivial). We examined then the dependence of the statistical quantities used in the analysis of the local structure for N = 864 and N = 2048 CO 2 molecules, and the results show no dependence on N .…”

Section: Simulation Detailsmentioning

confidence: 99%

Assessment of the Spatial Distribution in Sub- and Supercritical CO₂ Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis

Idrissi¹,

Vyalov²,

Damay³

et al. 2009

J. Phys. Chem. B

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The nearest neighbor approach was used to characterize the local structure of CO(2) fluid along its coexistence curve (CC) and along the critical isochore (CI). The distributions of the distances, orientations, and interaction energies between a reference CO(2) molecule and its subsequent nearest neighbors were calculated. Our results show that the local structure may be resolved into two components or subshells: one is characterized by small radial fluctuations, the parallel orientation and a dominance of the attractive part of both the electrostatic (EL) and Lennard-Jones (LJ) to the total interaction energy. Conversely, the second subshell is characterized by large radial fluctuations, a perpendicular orientation, and a concomitant increase of the repulsive contribution of the EL interaction and a shift to less attractive character of the LJ contribution. When the temperature increases along the liquid-gas CC, the first subshell undergoes large changes which are characterized by an obvious increase of the radial fluctuations, by an increase of the random character of the orientation distribution except for the first nearest neighbor which maintains its parallel orientation, and by a drastic decrease of the EL interaction contribution to the total interaction energy. When the temperature is close to the critical isochore, the local structure is no longer resolved into two subshells. Starting from the idea that the profile of vibration modes is sensitive to the local structure as revealed from the nearest neighbor approach, the hypothesis that the CO(2) vibration profile may be deconvoluted into two contributions is discussed in a qualitative manner.

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Section: Simulation Detailsmentioning

confidence: 99%

Assessment of the Spatial Distribution in Sub- and Supercritical CO₂ Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis

Idrissi¹,

Vyalov²,

Damay³

et al. 2009

J. Phys. Chem. B

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A high-pressure high-temperature setup for in situ Raman spectroscopy of supercritical fluids

Louvel

Bordage

Silva-Cadoux

et al. 2015

Journal of Molecular Liquids

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Analysis of the transverse and the longitudinal pseudodiffusion of CO2 in sub- and supercritical states: A molecular-dynamics analysis

Idrissi

Longelin

Damay

et al. 2006

The Journal of Chemical Physics

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We have performed molecular-dynamics simulations of CO(2) system along the gas-liquid coexistence curve and on the isochore 94.22 cm(3) mol(-1) (which corresponds to the critical isochore). The calculation has been carried out in order to analyze the diffusion of CO(2) and particularly to figure out how the diffusion coefficient may be decomposed along the molecular axes. This makes it possible to analyze the anisotropy of the diffusion along these axes and to shed light on the microscopic changes which accompany such behavior. This anisotropy is traced back to the effect of the translation-rotation coupling (TRC) along the molecular axes. Along the liquid-gas coexistence curve, the pseudolongitudinal diffusion is found to be more rapid than the transverse one. The opposite trend is found along the isochore 94.22 cm(3) mol(-1). The role of the local structure was explored by calculating intermediate scattering function and the autocorrelation functions for the forces acting along the molecular axes. It is shown that the strength of the TRC effect is correlated to the difference between the relaxation times of the local structure, that of the reorientation along the molecular axes, and that of the translational motion. The analysis of the correlation time and the average mean square force along the longitudinal and transverse directions confirms the anisotropy of the local environment that determines the translational dynamics of a molecule.

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Low-frequency Raman spectra of sub- and supercritical CO2: Qualitative analysis of the diffusion coefficient behavior

Cited by 4 publications

References 50 publications

Assessment of the Spatial Distribution in Sub- and Supercritical CO₂ Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis

Assessment of the Spatial Distribution in Sub- and Supercritical CO₂ Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis

A high-pressure high-temperature setup for in situ Raman spectroscopy of supercritical fluids

Analysis of the transverse and the longitudinal pseudodiffusion of CO2 in sub- and supercritical states: A molecular-dynamics analysis

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Low-frequency Raman spectra of sub- and supercritical CO2: Qualitative analysis of the diffusion coefficient behavior

Cited by 4 publications

References 50 publications

Assessment of the Spatial Distribution in Sub- and Supercritical CO2 Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis

Assessment of the Spatial Distribution in Sub- and Supercritical CO2 Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis

A high-pressure high-temperature setup for in situ Raman spectroscopy of supercritical fluids

Analysis of the transverse and the longitudinal pseudodiffusion of CO2 in sub- and supercritical states: A molecular-dynamics analysis

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Product

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Assessment of the Spatial Distribution in Sub- and Supercritical CO₂ Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis

Assessment of the Spatial Distribution in Sub- and Supercritical CO₂ Using the Nearest Neighbor Approach: A Molecular Dynamics Analysis