Data for: Density Functional Study of the Thermodynamic Properties and Phase Diagram of the Magnesium Hydride

Phase Diagram for Magnesium Hydride Polymorph

Data for: Density Functional Study of the Thermodynamic Properties and Phase Diagram of the Magnesium Hydride

Phase Diagram for Magnesium Hydride Polymorph

Divergence-Free Description of Molecular Rotation in Cartesian Coordinates: The Axis-Rotation Formula and some of its Applications to Computational Chemistry

in this work, based on simple algebraic manipulations, the divergence-free description of molecular rotations is revisited using the axis-rotation formula for the rigid-body system. The so-called axis-rotation formula is useful in various fields of computational chemistry, including molecular simulations, graphical rendering and group theory, allowing more convenient ways to construct and to manipulate the atomic or fragment structures of rotations. It is shown that the analytical expression of the axis-rotation operator facilitates obtaining the symmetry operator in analytical form, which is useful in the determination of group symmetries of molecules and the adaptation to the symmetry of atomic and molecular orbitals

Guest-host coupling and anharmonicity in clathrate hydrates

We present a review of our work on the dynamics of clathrate hydrates (gas hydrates). The experimental results obtained with inelastic neutron scattering are compared with molecular-dynamics calculations. The vibrations of the guest molecules and their coupling to the cages is found to depend critically on the size, shape and electrostatic properties of the encaged guest. Atoms like xenon, that are large enough to fill the cages, show close-to-harmonic behaviour and couple strongly to the cage vibrations. Small atoms and molecules fully explore the anharmonicities of the potential within the cage, in particular at low frequencies and low temperatures. Their dynamic response is broad in energy and they couple weakly to the cage vibrations. The relevance of the microscopic dynamics for cage stability and the glass-like thermal conductivity is discussed. We equally place the observed dynamic peculiarities into the broader context of vibrations in disordered systems. Raman spectroscopic results on internal guest vibrations at high frequencies reflect also the influence of guest-host interactions and are discussed in the framework of the loose-cage tight-cage model

Possible dual-charge-carrier mechanism of surface conduction on gamma-alumina

We cast a dual-charge-carrier model of surface conductance on gamma-alumina in mathematical form. We then carry out first-principles calculations for various possible atomic-scale structures of the low- and high-temperature charge-carrier interactions with the gamma-alumina surface to estimate the values of the energy parameters in the dual-charge-carrier model. By comparing the values of these energy parameters as determined by first-principles calculations to those obtained by fitting the mathematical form of the dual-charge-carrier model to experimental data, new insight is gained into the nature of the charge-carrier species. The results support the hypothesis that the intrinsic hydrogen content and surface moisture of gamma-alumina provide a possible explanation of the observed thermal dependence of surface conductance