Electronic stucture of methane hydrate studied by Compton scattering

Abstract

High-resolution Compton scattering spectra of methane, methane hydrate, and ice were measured using incident photon energy of 56.4 keV at beamline ID15B of the European Synchrotron Radiation Facility. The experimental Compton profiles are compared to calculations employing density-functional theory using model atomic clusters. The hydrate has a cagelike structure built up from water molecules and the related Compton profile is observed to change apparently when compared to hexagonal ice. Furthermore, the influence of the guest-host interactions between the methane molecules and the water molecules of the cages on the Compton profile is discussed.

Pressure-induced transitions in solid nitrogen: Role of dispersive interactions

“…III B, but it is not the only one. In CRYSTAL, the truncation of infinite lattice sums is controlled by five thresholds, T1 to T5, which are set here to 16,12,12,15,30. Note, in particular, that a tight value T1 = 16 must be adopted for a reliable description of CPs and related quantities, instead of the default value of 6, which is adequate for most other purposes: this is necessary to generate geometrical information on a sufficiently large set of lattice vectors.…”

“…5,6 In recent years, this technique has been applied to the study of many "disordered" systems; [7][8][9][10][11] nevertheless, its main field of application still remains that of crystalline compounds, whose intrinsic anisotropy constitutes a source of additional information. [12][13][14][15][16][17] The importance of comparing accurate experimental and theoretical EMDs is clear from the above: this is precisely the aim of this study, which concerns the prototypical case of crystalline silicon. It is motivated by two elements of novelty in the respective areas.…”

Charge transfer in silicon clathrates studied by Compton scattering

“…Later on methane hydrate, which is isostructural to the type-I silicon clathrates, was studied by Compton scattering with the focus on guesthost interactions between the methane guest molecules and the water network. 21 The Compton profile ͑CP͒ J͑p z ͒ is proportional to the double differential cross section of inelastic x-ray scattering within the impulse approximation 24 and given by J͑p z ͒ = ͵͵ ͑p͒dp x dp y .…”

Intramolecular structure and energetics in supercooled water down to 255 K

“…Thus, the Compton profile is related to the ground state electron momentum density r(p) and is very sensitive to single particle properties and small changes in the intra-and intermolecular bond geometry in molecular systems, 40 in particular in hydrogen-bonded systems such as liquid, confined and supercritical water, [41][42][43][44][45] structure and energetics of ice [46][47][48][49] and two-component systems. 37,[50][51][52][53] Here, p q denotes a scalar electron momentum variable. Since the electron momentum density is probed, Compton scattering allows accessing the expectation value of the electron kinetic energy hE kin i via 48,52 E kin h i¼ 3 m…”