A minimal-parameter tight-binding theory incorporating explicit use of nonorthogonality of the basis is used to generate a transferable scheme for germanium. Good results are obtained for high-pressure bulk phases and vibrational frequencies. Diamond structure is found to be the ground state even when compared with the clathrate structure. The results for clusters show good agreement with ab in...

We report a new lattice structure of the ionic clathrate hydrate of tetra-n-butylammonium bromide induced by guest CO2 molecules, which is found to provide high CO2 storage capacity. The structure was characterized by a set of methods, including single crystal X-ray diffraction, NMR, and MD simulations.

Under ambient conditions, water freezes to either hexagonal ice or a hexagonal/cubic composite ice. The presence of hydrophobic guest molecules introduces a competing pathway: gas hydrate formation, with the guests in clathrate cages. Here, the pathways of the phase transitions are sought as sequences of states with coexisting phases, using a generalized replica exchange algorithm designed to s...

Methane hydrate dissociation at negative temperatures was studied experimentally for different artificial and natural samples, differing by macro- and micro-structural parameters. Four characteristic dissociation types are discussed in the paper. The internal kinetics of artificial granule gas hydrates and clathrate hydrates in coal is dependent on the porosity, defectiveness and gas filtration...

This paper reports the influence of sucrose on the preservation of CO2 hydrate crystal samples. The particle diameter of hydrate samples were 1.0 and 5.6-8.0 mm. Mass fraction of sucrose in the sample was 0.16. The samples were stored at the aerated condition under atmospheric pressure and at the temperature of 253 or 258 K. The results indicated that the mass fractions of CO2 hydrate in the sa...

Introduction: Recently, a small quantity of methane (≈ 10 ppbv) has been detected in the atmosphere of Mars by the Planetary Fourier Spectrometer (PFS) onboard the Mars Express spacecraft [1]. The photochemical mean lifetime of the martian atmospheric methane is ≈ 300-600 years [1,2], and so it should not still exist today. To explain its presence, several scenarios have been invoked, like the ...

The thermal properties and transition behavior of the host-guest inclusion compounds: urea, thiourea, Dianin’s compound, clathrate hydrates and hydroquinone have been reviewed. In particular, we summarize their thermal conductivities, heat capacities and transitions at high pressures. Two of the systems: urea inclusion compounds and clathrate hydrates, show unusual glass-like thermal conductivi...

Methane can be stored in tea clathrates, that is kinetics of methane clathrate formation can be significantly accelerated (90% saturation uptake in 20 min) by ingredients (polyphenols and saponins) in tea infusions with a volumetric capacity of up to 172 v/v.

The stability of hydrate frameworks is influenced by guest molecules capable of hydrogen bonding with surrounding water molecules. Four remarkable features from the ammonium fluoride incorporation into a crystalline hydrate matrix provide important information on the thermodynamic stability, formation kinetics, structural characteristics, and molecular behavior in clathrate hydrate systems.

In this paper, we report the first grand canonical Monte Carlo simulation study aiming at characterizing competitive trapping of CH4 and C2H6 molecules into clathrate hydrates under temperature conditions typical those encountered surface Titan. Various compositions fluid in contact with phase have been considered simulations, including pure methane, ethane, mixed fluids made various methane/et...