Anomalous behavior of the vibrational spectrum of the high-pressure δ phase of nitrogen: A second-order transition

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

doi:10.1103/physrevlett.71.2252

Cited by 54 publications

(30 citation statements)

References 17 publications

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“…In accordance with the results of Ref. 4, Westerhoff et al 5 have found an anomaly in the pressure dependence of the linewidth of the 1 vibron, which corresponds to the a sites, at a pressure of 12 GPa at room temperature.…”

Section: Introductionsupporting

confidence: 79%

“…For the xϭ0.75 we estimate the temperature of the break to be 0 to 30 K above the second order transition temperature of pure N 2 . 4 No additional Raman peaks have been observed near the break. Since the frequencies have been measured in temperature steps of about 10 K and considering the accuracy, a small hysteresis of a few K cannot be excluded.…”

Section: B Second Order Transitionmentioning

confidence: 97%

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Raman spectra and phase behavior of the mixed solidN2−Arat high pressure

Kooi

Schouten

1998

Phys. Rev. B

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Link to publication Citation for published version (APA):Kooi, M. E., & Schouten, J. A. (1998). Raman spectra and phase behavior of the mixed solid N2-Ar at high pressure. Physical Review B, 57, 10407-10413. DOI: 10.1103/PhysRevB.57.10407 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. Download date: 11 May 2018Raman spectra and phase behavior of the mixed solid N 2 -Ar at high pressure The mixed solid N 2 -Ar has been studied for x͓N 2 ͔у0.75, 130ϽTϽ470 K, and 0Ͻ pр20 GPa. A transition, very similar to the second order transition observed in pure ␦-N 2 , is still present in the mixed solid at 75 mol % N 2 . An anomalous increase of the slope in a p-T scan has been found, which is attributed to a redistribution of the Ar atoms near this transition. Although within the ␦* phase the Ar atoms are mainly located at the a sites, the distribution of the Ar atoms about the sites depends on temperature and pressure. Also at these high pressures the Ar atoms are able to move through the lattice. The inhomogeneous broadening of the vibrational signal in the ␦* phase has been observed also at low temperatures. The phase diagram of the mixture has been studied. The ␦-␤ transition of pure N 2 is shifted to lower temperatures in the mixture, while the ␤-fluid transition is shifted to higher temperatures. The results are in agreement with computer simulations.

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Section: Introductionsupporting

confidence: 79%

Section: B Second Order Transitionmentioning

confidence: 97%

Raman spectra and phase behavior of the mixed solidN2−Arat high pressure

Kooi

Schouten

1998

Phys. Rev. B

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“…The splitting of the frequency of the molecules at the disks sites at low temperature, caused by the difference in localization, has not been reported in Ref. 18. This might be due to the experimental resolution, but needs further investigation.…”

Section: Discussionmentioning

confidence: 75%

“…Scheerboom and Schouten 18 observed that the linear behavior of 2 of the ␦ loc structure is slightly steeper than that of the ␦ rot structure ͑Fig. 3͒.…”

Section: Discussionmentioning

confidence: 99%

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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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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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Anomalous behavior of the vibrational spectrum of the high-pressure δ phase of nitrogen: A second-order transition

Abstract: Anomalous behavior of the vibrational-spectrum of the high-pressure delta-phase of nitrogen : a second-order transition Scheerboom, M.I.M.; Schouten, J.A.

Cited by 54 publications

References 17 publications

Raman spectra and phase behavior of the mixed solidN2−Arat high pressure

Raman spectra and phase behavior of the mixed solidN2−Arat high pressure

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

Solid Nitrogen at Extreme Conditions of High Pressure and Temperature

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