The structure of N2 at 49 kbar and 299 K

Cromer, D. T.; Mills, R. L.; Schiferi, D.; Schwalbe, L.A.

doi:10.1107/s0567740881002070

Cited by 121 publications

(28 citation statements)

References 12 publications

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“…A structural search within several databases with corresponding lattice parameters in the tetragonal crystal system showed that HP-LaN is isotypic with a high-pressure polymorph of BaO and homeotypic with PH 4 X (X ¼ Br, I) crystallizing in a tetragonally distorted CsCl-type structure. Depending on pressure, the corresponding HP-phases of nitrogen (d-and e-N 2 ) 32,33 have also been refined together with ambient or/and HP-LaN in order to obtain the correct lattice parameters upon Rietveld refinement of both LaN phases (see Table I). In between the starting and final pressure of transformation (22.8-26.5 GPa), both LaN phases were refined simultaneously.…”

Section: Introductionmentioning

confidence: 99%

Reversible high-pressure phase transition in LaN

Schneider¹,

Baumann²,

Salamat³

et al. 2012

Journal of Applied Physics

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In situ high-pressure X-ray powder diffraction experiments on LaN up to 60.1 GPa at ambient temperature in a diamond-anvil cell revealed a reversible, first-order structural phase transition starting at $22.8 GPa and completed at $26.5 GPa from the ambient cubic phase (Fm 3m, no. 225) to a tetragonal high-pressure phase (P4/nmm, no. 19, a ¼ 4.1060(6), c ¼ 3.0446(6) Å , Z ¼ 2, wR p ¼ 0.011), which has not been claimed in theoretical predictions. HP-LaN is isotypic with a high-pressure polymorph of BaO, which crystallizes in a tetragonally distorted CsCl-type structure. The phase transition is accompanied by a volume collapse of about 11% which corresponds well with the reported data on HP-BaO. A linear extrapolation of the c/a ratio of the tetragonally distorted CsCl-type sub-cell reaches a value c/a ¼ 1 of cubic CsCl-type HP-LaN at 91(12) GPa. In addition, the compressibility of LaN was investigated and resulted in a bulk modulus for the ambient pressure phase of

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Section: Introductionmentioning

confidence: 99%

Reversible high-pressure phase transition in LaN

Schneider¹,

Baumann²,

Salamat³

et al. 2012

Journal of Applied Physics

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“…2͑a͔͒. Although the nature of the orientational disorder could not be experimentally established, 15 computer simulations 16,17 indicate it is highly dynamical. The unit cell of the phase 11 ͓R3c, Fig.…”

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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“…[27][28][29] The two molecules on the a sites are completely orientational disordered and the six molecules on the c sites have a random orientation in a plane normal to the faces of the unit cell. Therefore, the Raman spectrum consists of two distinct peaks, corresponding to the frequencies of the molecules on the a and c sites, respectively.…”

Section: Figmentioning

confidence: 99%

Calculation of the vibrational linewidth and line shape of Raman spectra using the relaxation function. I. Method and application to nitrogen

Kooi¹,

Smit²,

Michels³

et al. 2000

The Journal of Chemical Physics

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. (2000). Calculation of the vibrational linewidth and line shape of Raman spectra using the relaxation function : I. method and application to nitrogen. Journal of Chemical Physics, 112(3), 1395-1403. DOI: 10.1063/1.480693 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. The spectral line shape of the fundamental vibration of nitrogen is calculated from molecular dynamics simulations by determining the Fourier transform of the relaxation function. It has been applied to the fluid phase at various pressures and temperatures, and to solid ␦-N 2 . The validity of the assumption that the spectrum at relatively high temperatures and pressures can be calculated by assuming that these systems are in the fast modulation regime (⌬ c Ӷ1), has been verified. A deviation of the vibrational line shape from the motional narrowing limit has been found for fluid nitrogen at low pressure, with a Kubo parameter, ⌬ c , equal to 0.23, and for the vibrational line of the molecules on the a sites in ␦-N 2 , with ⌬ c equal to 0.075. It is concluded that the value of the Kubo parameter is not an unambiguous criterion for the fast modulation regime. Moreover, a detailed comparison reveals a difference in the dynamical behavior of the molecules on the a and c sites. It is shown that this procedure can also be used if one does not know whether or not closely spaced lines are to be expected. The present procedure is suited to calculate line shapes in the intermediate Kubo regime, e.g., in concentrated mixtures, where no simple relations are available. Finally it is shown that in nitrogen at low density and 126 K the ratio of the correlation time of the frequency autocorrelation function and the dephasing time is smaller than in CH 3 I, where the n dependence of the vibrational overtone is subquadratic.

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The structure of N2 at 49 kbar and 299 K

Cited by 121 publications

References 12 publications

Reversible high-pressure phase transition in LaN

Reversible high-pressure phase transition in LaN

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

Calculation of the vibrational linewidth and line shape of Raman spectra using the relaxation function. I. Method and application to nitrogen

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