In this paper the diffusion Monte Carlo method is applied to the confined hydrogen atom with different confinement geometries. This approach is validated using the much studied spherical and cylindrical confinements and then applied to cubical and squared ones, for which data are not available, as new applications of the method relevant to solid state physics. The energy eigenvalues of the ground state and one low-lying excited state are reported as a function of the characteristic confinement length.

In this paper, the thermal decomposition kinetics of a class of minerals that we call White Soft Minerals (WSMs) is studied by means of theoretical and experimental methods, in connection to the transport of extraterrestrial organic matter to Earth and the possible use of the decomposition reaction in the characterization of these minerals in space. WSMs include, under a single denomination, carbonates and sulphates of Mg, Fe, and Ca. To improve the present knowledge of the properties of such materials, we use the following techniques: kinetic models for chemical decomposition, atmospheric entry models, spectroscopy, and gravimetric analyses. Model results show that the atmospheric entry of WSM grains is strongly affected by their thermal decomposition. The decomposition reaction, being strongly endothermic, tends to significantly lower the grain temperature during the atmospheric entry, especially at high altitudes and for grazing entries. A previously proposed infrared spectroscopic technique to evaluate the degree of advancement of the reaction is found to be in good agreement with gravimetric measurements for calcium carbonate. The numerical model developed for the atmospheric entry scenarios is used to interpret experimental results. These main findings show that an additional contribution to the reaction enthalpy is needed to reproduce the experimental results, suggesting that the present theoretical model needs improvements such as the account of gas diffusion in the materials.

The diffusion Monte Carlo method with symmetry-based state selection is used to calculate the quantum energy states of H 2 + confined into potential barriers of atomic dimensions (a model for these ions in solids). Special solutions are employed, permitting one to obtain satisfactory results with rather simple native code. As a test case, u 2 Π and g 2 Π states of H 2 + ions under spherical confinement are considered. The results are interpreted using the correlation of H 2 + states to atomic orbitals of H atoms lying on the confining surface and perturbation calculations. The method is straightforwardly applied to cavities of any shape and different hydrogen plasma species (at least one-electron ones, including H) for future studies with real crystal symmetries.