Orientational behavior of solid nitrogen at high pressures investigated by vibrational Raman spectroscopy

Scheerboom, M. I. M.; Schouten, J. A.

doi:10.1063/1.472121

Cited by 34 publications

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“…The coefficients of the fits through the data of the anisotropic, Etters, and core potential, next to the experimentally 19 determined coefficients, are given in Table I. Although the difference in coefficients is small, the results obtained with the Etters and anisotropic potential are in better agreement with experiment.…”

Section: Discussionmentioning

confidence: 69%

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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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Section: Discussionmentioning

confidence: 69%

“…The angle d depends on the angles of the unit cell. An extensive Raman study performed by Scheerboom and Schouten 18,19 revealed a second-order transition within the ␦ phase. Figure 3 shows the behavior of the frequencies of the spheres ( 1 ) and the disks ( 2 ) at 5.9 GPa.…”

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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“…[8][9][10][11]. It can be seen directly that the decrease of the line width is for the greater part caused by the behavior of c :⌬ nitrogen and ⌬ argon decrease only Ϸ6% and Ϸ2%, respectively, while the correlation time is reduced to about half at the transition.…”

Section: Discussionmentioning

confidence: 87%

“…Unfortunately one cannot compare these results with the shift in solid pure nitrogen, i.e., the shift of one nitrogen molecule in a matrix of other nitrogen molecules, because of resonance coupling ͑RC͒. 8 At low pressure, this RC coupling is responsible for a continuous behavior of the shift at the fluid-solid ͑␤͒ phase transition. 11 At high pressure this RC is probably absent along the ␤-melting line.…”

Section: Introductionmentioning

confidence: 99%

“…11 At high pressure this RC is probably absent along the ␤-melting line. 8 In this paper, new experimental results are given for the line shift and linewidth of nitrogen in the solid phase and for nitrogen diluted in solid argon, just above the fluid-solid phase transition at ambient temperature and, consequently, at high pressure. It is seen that the solidification at these conditions has a marked influence on the Raman line, also for pure nitrogen.…”

Section: Introductionmentioning

confidence: 99%

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The vibrational frequency of nitrogen near the fluid–solid transition in the pure substance and in mixtures

Michels

Kooi

Schouten

1998

The Journal of Chemical Physics

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. (1998). The vibrational frequency of nitrogen near the fluid-solid transition in the pure substance and in mixtures. Journal of Chemical Physics, 108(7), 2695-2702. DOI: 10.1063/1.475699 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. At high densities intramolecular vibrations are strongly dependent on the interactions with the surrounding molecules. In this paper a study is made of the consequences of these interactions on the Raman Q-branch of nitrogen. In particular the difference between a disordered and an ordered surrounding is surveyed. For this purpose, high-resolution Raman spectroscopy has been performed at room temperature on pure nitrogen as well as on a dilute mixture of nitrogen in argon, around the fluid-solid phase transition of these systems, which occur at Ϸ2.5 GPa and at Ϸ 1.3 GPa, respectively. Going from the liquid to the solid phase, a positive jump in the line shift and a dramatical drop in the linewidth are seen in both systems at the transition pressure. For a better understanding of the underlying mechanisms, molecular dynamical simulations have been performed on corresponding model systems. The results of these calculations are in fair agreement with the experimental data and reveal the reasons for the discontinuities. Although the average distance of the nearest neighbor molecules around the nitrogen molecule increases, the distance to the nearest neighbor molecules in line with the molecular axis of the nitrogen decrease at the phase transition. This results in a positive jump in the frequency. Further, the time-autocorrelation function of the vibration frequency has a long persisting positive tail in the fluid phase. This behavior is absent in the solid phase. Even more important is that this function has negative values during a substantial time interval in the solid phase. As a result, the correlation time is greatly reduced at the phase transition, which results in an important reduction of the linewidth as well. Finally, it is proven that also in the solid phase the nitrogen is really dissolved in argon.

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Solid Nitrogen at Extreme Conditions of High Pressure and Temperature

Goncharov

Gregoryanz

2005

ChemInform

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We review the phase diagram of nitrogen in a wide pressure and temperature range. Recent optical and x-ray diffraction studies at pressures up to 300 GPa and temperatures in excess of 1000 K have provided a wealth of information on the transformation of molecular nitrogen to a nonmolecular (polymeric) semiconducting and two new molecular phases. These newly found phases have very large stability (metastability) range. Moreover, two new molecular phases have considerably different orientational order from the previously known phases. In the iota phase (unlike most of other known molecular phases), N 2 molecules are orientationally equivalent. The nitrogen molecules in the theta phase might be associated into larger aggregates, which is in line with theoretical predictions on polyatomic nitrogen.

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Orientational behavior of solid nitrogen at high pressures investigated by vibrational Raman spectroscopy

Cited by 34 publications

References 47 publications

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

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

The vibrational frequency of nitrogen near the fluid–solid transition in the pure substance and in mixtures

Solid Nitrogen at Extreme Conditions of High Pressure and Temperature

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