Room temperature Raman scattering studies of external and internal modes of solid nitrogen at pressures 8≤<i>P</i>≤54 GPa

Schneider, Harald; Hafner, Wolfgang; Wokaun, Alexander; Olijnyk, H.

doi:10.1063/1.462356

Cited by 73 publications

(81 citation statements)

References 25 publications

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“…A MD study 18 shows that it should be negative, but that the effect should also be less than 10%. It is likely that this fraction will not increase at high pressures 26 because a recent experiment with an isotropic dilution on solid N 2 did not reveal any resonance coupling effect on the Raman shift of the 2 mode below 20 GPa. This 2 mode is the same as the fluid mode along the ␦-fluid melting line.…”

Section: Methodsmentioning

confidence: 99%

Computer simulations of the linewidth of the Raman Q-branch in fluid nitrogen

Michels

Scheerboom

Schouten

1995

The Journal of Chemical Physics

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General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. By means of molecular dynamical simulations, the width of the Raman line in fluid N 2 is calculated at room temperature and pressures up to the melting line. The results are compared with experimental results for the linewidth and for the dephasing time. Detailed information is given about the relaxation mechanism of the vibrational frequency. For instance, a marked influence of the vibration-rotation coupling is seen, in particular at high pressures. Moreover, the time correlation function of the frequency reveals a long time behavior at high pressures. From a comparison of the simulated change in vibrational frequency as a function of pressure with experimental data for the line shift, an estimate is made for the contribution of the so-called ''attractive part'' to that shift.

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Section: Methodsmentioning

confidence: 99%

Computer simulations of the linewidth of the Raman Q-branch in fluid nitrogen

Michels

Scheerboom

Schouten

1995

The Journal of Chemical Physics

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“…A diamond anvil cell (DAC) was used for pressure generation. Experiments were initially performed with nitrogen as a pressure medium and then, in order to avoid the Raman scattering of solid nitrogen, 21 continued with the standard 4:1 methanol-ethanol mixture (M/E) as well as with helium; the latter ensures the best hydrostatic conditions in combination with low background. In all experiments, pressures were measured by the ruby luminescence method.…”

Section: Raman Spectroscopymentioning

confidence: 99%

Effect of pressure on the Raman modes of antimony

et al. 2006

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The effect of pressure on the zone-center optical phonon modes of antimony in the A7 structure has been investigated by Raman spectroscopy. The Ag and Eg frequencies exhibit a pronounced softening with increasing pressure, the effect being related to a gradual suppression of the Peierls-like distortion of the A7 phase relative to a cubic primitive lattice. Also, both Raman modes broaden significantly under pressure. Spectra taken at low temperature indicate that the broadening is at least partly caused by phonon-phonon interactions. We also report results of ab initio frozenphonon calculations of the Ag and Eg mode frequencies. Presence of strong anharmonicity is clearly apparent in calculated total energy versus atom displacement relations. Pronounced nonlinearities in the force versus displacement relations are observed. Structural instabilities of the Sb-A7 phase are briefly addressed in the Appendix.

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“…At still higher pressure the -␦ transition is found, which has been examined with x-ray diffraction 11,12 and Raman scattering. 13,14 The ␦ phase ( Pm3n) ͑Refs. 11, 12, and 15͒ is the orientationally disordered phase.…”

Section: Introductionmentioning

confidence: 99%

ɛ-δ phase transition of nitrogen and the orientational behavior of the second-order transition within the δ phase: A Monte Carlo study at 7.0 GPa

1998

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Link to publication Citation for published version (APA):Mulder, A., Michels, J. P. J., & Schouten, J. A. (1998). epsilon-delta phase transition of nitrogen and the orientational behavior of the second-order transition within the delta phase: A Monte Carlo study at 7.0 GPa. Physical Review B, 57, 7571-7580. DOI: 10.1103/PhysRevB.57.7571 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Monte Carlo simulations have been performed with an improved nitrogen-nitrogen potential at 7.0 GPa, to study the behavior near the -␦ phase transition, to calculate the vibrational frequencies in the ␦ phase, and to examine the second-order phase transition within the ␦ phase. The -phase structure transformed to the ␦-phase structure at 140 K, whereas the ␦-phase structure is metastable below this temperature. The second-order transition could be detected in several ways. At high temperature the orientational behavior of all molecules is highly dynamical with weakly preferred orientations. At the second-order transition the molecules at the disk sites become localized with different orientations, whereas the orientational behavior of the molecules at the sphere sites does not change. The localization causes the frequency of the disk sites to split with an intensity of 1:2, and influences the frequency of the sphere sites. The frequency behavior calculated with this model system resembles the experimental behavior. Additional calculations revealed that the anisotropic energy term as well as the Coulomb term of the intermolecular potential influence not only the stability of the -phase structure, but also the orientational behavior, and thus the nature, of the second-order phase transition.

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Room temperature Raman scattering studies of external and internal modes of solid nitrogen at pressures 8≤P≤54 GPa

Cited by 73 publications

References 25 publications

Computer simulations of the linewidth of the Raman Q-branch in fluid nitrogen

Computer simulations of the linewidth of the Raman Q-branch in fluid nitrogen

Effect of pressure on the Raman modes of antimony

ɛ-δ phase transition of nitrogen and the orientational behavior of the second-order transition within the δ phase: A Monte Carlo study at 7.0 GPa

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