Orientational correlations in high-pressure fluid oxygen and nitrogen

Temleitner, László; Pusztai, László; Akahama, Yuichi; Kawamura, Haruki; Kohara, Shinji; Ohishi, Yasuo; Takata, Masaki

doi:10.1103/physrevb.78.014205

Cited by 16 publications

(8 citation statements)

References 24 publications

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“…The existence of a polymeric liquid would be unambiguously evidenced by structure factor measurements. So far this information is limited on fluid nitrogen to 2.5 GPa at ambient temperature [12]. Extending the structural investigation into the megabar range and under a few thousand kelvin temperature represents a formidable technical challenge.…”

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confidence: 99%

Melting Curve and Liquid Structure of Nitrogen Probed by X-ray Diffraction to 120 GPa

et al. 2017

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Synchrotron x-ray diffraction measurements of nitrogen are performed up to 120 GPa to determine the melting curve and the structural changes of the solid and liquid phases along it. The melting temperature exhibits a monotonic increase up to the triple point where the epsilon molecular solid, the cubic gauche covalent solid, and the fluid meet at 116 GPa, 2080 K. Above, the stability of the cubic gauche phase induces a sharp increase of the melting curve. The structural data on liquid nitrogen show that the latter remains molecular over the whole probed domain, which contradicts the prediction of a liquid-liquid transition at 88 GPa, 2000 K. These findings thus largely revisit the phase diagram of hot dense nitrogen and challenge the current understanding of this model system.

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confidence: 99%

Melting Curve and Liquid Structure of Nitrogen Probed by X-ray Diffraction to 120 GPa

et al. 2017

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“…There is a good correspondance between this S mol (Q) and the one we determined at 1 GPa, 800 K (ρ = 24.6 ± 1.1 molecules.nm −3 ), except that the latter has broader peaks, which is likely due to the effect of the higher temperature. The shape of S mol (Q) is at first glance, very similar to that of a liquid with no or weak orientational correlations such as H 2 [26,59], N 2 [60,61] and O 2 [61,62]. In dense monatomic liquids it is empirically found that the position of the maximum of the FDP, Q M is related to the density ρ through the relation Q M 4.4(4πρ/3) 1/3 [63], and thus (Q M /Q M 0 ) 3 ρ/ρ 0 where Q M 0 and ρ 0 correspond to a reference state.…”

Section: A Experimentsmentioning

confidence: 83%

Structure of liquid ammonia at high pressures and temperatures

et al. 2019

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The structure of liquid ammonia (NH3) is investigated from 1 to 6.3 GPa and up to 800 K by means of synchrotron x-ray diffraction (XRD) and ab initio molecular dynamics (AIMD) simulations. The XRD data are used to extract the molecular structure factor S mol (Q), pair distribution function (PDF) g mol (r), and the density of NH3. There is an excellent agreement between present S mol (Q) and g mol (r) at our lowest density and those reported in reference neutron experiments. Our densities agree better with the equation of state of Tillner-Roth et al. [1] than with more recent equation of state (EoS) models. The experimental structure factor and PDF are well reproduced by AIMD simulations using either the BLYP or the PBE exchange-correlation functional. The shapes of S mol (Q) and g mol (r) vary little over the investigated pressure range and suggest a compact liquid with weak orientational correlations between molecules, which is corroborated by the coordination number varying from 12.7 to ∼14. The simulations are used to study the evolution of the site-site pair distribution functions, which reveals that the number of H-bonds per molecule (between 1.5 and 2) do not evolve with density, and that the distribution of H atoms around N atoms becomes more and more anisotropic with pressure.

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“…Molecular pairs were classified by the number of ligands, belonging to one and the other of the two molecules between these planes; this way, six "original" orientational groups arise. 17,18 It was demonstrated that well recognizable arrangements can easily be monitored such as "parallel"/"antiparallel," "T-shaped" or "chainlike. ͑2͒ Second, the two types of ligands ͑hydrogen and halogen atoms͒ were distinguished; note that this is our new extension to the original method.…”

Section: B Calculation Of Orientational Correlation Functionsmentioning

confidence: 99%

Extended orientational correlation study for molecular liquids containing distorted tetrahedral molecules: Application to methylene halides

Pothoczki

Temleitner

Pusztai

2010

The Journal of Chemical Physics

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The method of Rey [Rey, J. Chem. Phys. 126, 164506 (2007)] for describing how molecules orient toward each other in systems with perfect tetrahedral molecules is extended to the case of distorted tetrahedral molecules of c(2v) symmetry by means of introducing 28 subgroups. Additionally, the original analysis developed for perfect tetrahedral molecules, based on six groups, is adapted for molecules with imperfect tetrahedral shape. Deriving orientational correlation functions have been complemented with detailed analyses of dipole-dipole correlations. This way, (up to now) the most complete structure determination can be carried out for such molecular systems. In the present work, these calculations have been applied for particle configurations resulting from reverse Monte Carlo computer modeling. These particle arrangements are fully consistent with structure factors from neutron and x-ray diffraction measurements. Here we present a complex structural study for methylene halide (chloride, bromide, and iodide) molecular liquids, as possibly the best representative examples. It has been found that the most frequent orientations of molecules are of the 2:2 type over the entire distance range in these liquids. Focusing on the short range orientation, neighboring molecules turn toward each other with there "H,Y"-"H,Y" (Y: Cl, Br, I) edges, apart from CH(2)Cl(2) where the H,H-H,Cl arrangement is the most frequent. In general, the structure of methylene chloride appears to be different from the structure of the other two liquids.

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Orientational correlations in high-pressure fluid oxygen and nitrogen

Cited by 16 publications

References 24 publications

Melting Curve and Liquid Structure of Nitrogen Probed by X-ray Diffraction to 120 GPa

Melting Curve and Liquid Structure of Nitrogen Probed by X-ray Diffraction to 120 GPa

Structure of liquid ammonia at high pressures and temperatures

Extended orientational correlation study for molecular liquids containing distorted tetrahedral molecules: Application to methylene halides

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