The microscopic structure of the hydrogen liquids

Zoppi, M.; Bafile, Ubaldo; Celli, Milva; Cuello, G.J.; Formisano, F.; Guarini, Eleonora; Magli, R.; Neumann, Martin

doi:10.1088/0953-8984/15/1/313

Cited by 5 publications

(10 citation statements)

References 24 publications

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“…This is the isotropic component of the phenomenological potential given by Norman, Watts and Buck (NWB) [52]. The simulations were generally carried out using N = 500 classical particles and several Trotter numbers (P = number of beads in the classical isomorphic The open circles represent the para-hydrogen experimental data from [51] while the dots show the deuterium experimental data taken from [44].…”

Section: Comparison With Quantum Mechanical Simulation Resultsmentioning

confidence: 99%

“…The extended knowledge gained from the properties of liquid hydrogen permitted us to design a new neutron diffraction experiment on a standard reactor source. This experiment was carried out on the D4 diffractometer at ILL (Institute Laue-Langevin, Grenoble) and has allowed a reliable determination of S(Q), the microscopic COM structure factor of liquid para-hydrogen [51]. This is shown in figure 3 (open circles), together with the experimental results of liquid deuterium (dots) taken from [44].…”

Section: Neutron Diffraction Experiments On Liquid Hydrogenmentioning

confidence: 99%

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Microscopic structure of liquid hydrogen

Zoppi¹

2003

J. Phys.: Condens. Matter

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Hydrogen makes the simplest molecular liquid. Nonetheless, due to several different reasons, measuring its microscopic structure has been one of the most challenging tasks in neutron diffraction experiments. The recent development of modern pulsed neutron sources triggered a renewed experimental interest which, in turn, led to new knowledge and also to a more effective use of the classic reactor-based experimental data. The contemporary development of quantum mechanical computer simulation techniques, and a critical comparison among the results of different experiments using steady and pulsed neutron sources, resulted in a quantitatively reliable solution of the problem.

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Section: Comparison With Quantum Mechanical Simulation Resultsmentioning

confidence: 99%

Section: Neutron Diffraction Experiments On Liquid Hydrogenmentioning

confidence: 99%

Microscopic structure of liquid hydrogen

Zoppi¹

2003

J. Phys.: Condens. Matter

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“…For example, inelastic neutron scattering has been used to study molecular hydrogen confined within carbon-based materials, [3][4][5][6][7][8][9] clathrates, 10 hydrides, [11][12][13] metal-organic frameworks, [14][15][16][17][18][19] and zeolites. [19][20][21] Neutron scattering techniques are capable of probing the atomic-scale structure, 22,23 collective excitations, [24][25][26] rotational energy spectrum, 27,28 momentum distribution, [29][30][31] and diffusive dynamics 32 of condensed hydrogen, whether it is in a bulk phase or subjected to confinement.…”

Section: Introductionmentioning

confidence: 99%

Diffusive and rotational dynamics of condensed n-H₂confined in MCM-41

Prisk

Bryan

Sokol

2014

Phys. Chem. Chem. Phys.

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In this paper, we report an inelastic neutron scattering study of liquid and solid n-H2 confined within MCM-41. This is a high surface area, mesoporous silica glass with a narrow pore size distribution centered at 3.5 nm. The scattering data provides information about the diffusive and rotational dynamics of the adsorbed n-H2 at low temperatures. In the liquid state, the neutron scattering data demonstrates that only a fraction of the adsorbed o-H2 is mobile on the picosecond time scale. This mobile fraction undergoes liquid-like jump diffusion, and values for the residence time τ and effective mean-squared displacement 〈u(2)〉 are reported as a function of pore filling. In the solid state, the rotational energy levels of adsorbed H2 are strongly perturbed from their free quantum rotor behavior in the bulk solid. The underlying orientational potential of the hindered rotors is due to the surface roughness and heterogeneity of the MCM-41 pore walls. This potential is compared to the hindering potential of other porous silicas, such as Vycor. Strong selective adsorption makes the interfacial layer rich in o-H2, leaving the inner core volume consisting of a depleted mixture of o-H2 and p-H2.

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“…By a simple inspection of the center-of-mass static structure factors S c.m. ͑Q͒ of liquid H 2 [39] and D 2 [40], it was evident that the aforementioned incoherent approximation could not hold in this case. Thus Eq.…”

Section: B Extraction Of the H 2 Velocity Autocorrelation Function Smentioning

confidence: 93%

Microscopic self-dynamics in liquid hydrogen and in its mixtures with deuterium

et al. 2004

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We have measured the dynamic structure factor of liquid parahydrogen, pure and mixed with deuterium, in various thermodynamic conditions using incoherent inelastic neutron scattering. The experiments were carried out on TOSCA-II, a new time-of-flight, inverse-geometry, crystal-analyzer spectrometer. After an accurate data reduction, the high-energy parts of the neutron spectra recorded in backward scattering were studied through the modified Young and Koppel model, from which the mean kinetic energy values for a hydrogen molecule were estimated. In addition the low-energy parts of the neutron spectra recorded in forward scattering were analyzed in the framework of the Gaussian approximation and fitted through a Levesque-Verlet model for the velocity autocorrelation function. Thus various physical quantities are determined and compared with accurate path integral Monte Carlo simulations. Despite the excellent quality of these fits, the velocity autocorrelation functions derived from the forward-scattering data appear totally unable to properly describe the backward-scattering ones. These findings prove an unquestionable breakdown of the Gaussian approximation in semiquantum liquids. The present results appear of great interest and suggest further investigation on the limits of the widely used Gaussian approximation.

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The microscopic structure of the hydrogen liquids

Cited by 5 publications

References 24 publications

Microscopic structure of liquid hydrogen

Microscopic structure of liquid hydrogen

Diffusive and rotational dynamics of condensed n-H₂confined in MCM-41

Microscopic self-dynamics in liquid hydrogen and in its mixtures with deuterium

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The microscopic structure of the hydrogen liquids

Cited by 5 publications

References 24 publications

Microscopic structure of liquid hydrogen

Microscopic structure of liquid hydrogen

Diffusive and rotational dynamics of condensed n-H2confined in MCM-41

Microscopic self-dynamics in liquid hydrogen and in its mixtures with deuterium

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Diffusive and rotational dynamics of condensed n-H₂confined in MCM-41