We investigate the binding nature of the endohedral sodium atoms with the density functional theory methods, presuming that the clathrate I consists of a sheaf of one-dimensional connections of Na@Si(24) cages interleaved in three perpendicular directions. Each sodium atom loses 30% of the 3s(1) charge to the frame, forming an ionic bond with the cage atoms; the rest of the electron contributes...

In the crystal structure of the title organic salt, C(3)H(10)NO(+)·IO(4) (-)·C(12)H(24)O(6), the protonated 2-meth-oxy-ethanaminium (CH(3)OC(2)H(4)-NH(3) (+)) cation forms a 1:1 supra-molecular rotator-stator complex with the 18-crown-6 mol-ecule via N-H⋯O hydrogen bonds. The (CH(3)OC(2)H(4)-NH(3) (+)) group is attached from the convex side of the bowl-shaped crown, in contrast to similar ammon...

We report extended x-ray absorption fine-structure EXAFS studies of nand p-type Ba8Ga16Ge30 samples type-I clathrate at the Ga, Ge, and Ba K edges, to probe the local structure, particularly around the Ba atoms located inside 20and 24-atom cages Ba1 and Ba2 sites, respectively composed of Ga/Ge atoms. In agreement with diffraction analysis, we find Ba2 is off center, with a component in the bc ...

We have studied the diffusive mobility of hydrogen molecules confined in different size cages in clathrate hydrates. In clathrate hydrate H2 molecules are effectively stored by confinement in two different size cages of the nano-porous host structure with accessible volumes of about 0.50 and 0.67 nm diameters, respectively. For the processes of sorption and desorption of the stored hydrogen the...

Clathrate hydrates are supramolecular solids in which small, hydrophobic species are trapped inside a network of hydrogen-bonded water cages. While the best known examples are the natural gas hydrates, similar crystalline structures can also be formed from salts of tetra-n-butylammonium hydroxide (TBAOH). When TBAOH is reacted with medium to long chain carboxylic acids it produces surfactant co...

A composite ice nanotube inside a carbon nanotube has been explored by molecular-dynamics and grand canonical Monte Carlo simulations. It is made from an octagonal ice nanotube whose hollow space contains hydrophobic guest molecules such as neon, argon, and methane. It is shown that the attractive interaction of the guest molecules stabilizes the ice nanotube. The guest occupancy of the hollow ...

The phase diagram of water at negative pressures as obtained from computer simulations for two models of water, TIP4P/2005 and TIP5P is presented. Several solid structures with lower densities than ice Ih, so-called virtual ices, were considered as possible candidates to occupy the negative pressure region of the phase diagram of water. In particular the empty hydrate structures sI, sII, and sH...

Clathrate hydrates are crystalline structures composed of small guest molecules trapped into cages formed by hydrogen-bonded water molecules. In hydrate nucleation, water and the guest molecules may stay in a metastable fluid mixture for a long period. Metastability is broken if the concentration of the guest is above certain limit. We perform molecular dynamics (MD) simulations of supersaturat...

In the title compound, C(7)H(10)N(+)·ClO(4) (-)·C(12)H(24)O(6), the 4-methyl-anilinium cation inter-acts with an 18-crown-6 mol-ecule forming a rotator-stator-like structure through bifurcated N-H⋯(O,O) hydrogen bonds between the ammonium group of the cation and the O atoms of the crown ether mol-ecule. All three components of the structure possess mirror symmetry. The benzene ring is inclined ...