In this study, the elastic properties of two high-pressure polymorphs SiO2 nanostructure, stishovite and CaCl2-type, are obtained using Density Functional Theory in 0-80 GPa high pressure domain at zero temperature, based on reducing an interacting many-electron problem to a single-electron problem. It is shown that below 40 GPa, the stishovite phase is more stable; superior to this limit, the CaCl2-type phase becomes more stable, using Gibbs free energy method. Furthermore, the pressure dependence of the density, volume, bulk, and shear moduli were defined in the selected pressure domain.

This study reports the chemical composition of seven sandstones (OH1-OH7) from Ouargla desert in south-east of Algeria, then the investigation of these samples to be used as precursor for the hydrothermal synthetesis of piezoelectric mater in thin films form. Fourier-transform infrared (FT-IR) spectra shows the characteristic vibration bond peaks for the seven samples documenting the presence of quartz and calcite. Moreover, chemical composition of Ouargla sandstones has been determined by energy dispersive X-ray (EDS) and X-ray diffraction (XRD) allowed mainly a composition avrage major of 86.86 % α-quartz (SiO2) and minor of 13.14 % calcite (CaCO3). The EDS analysis revealed the presence of solid solution in the crystal lattice of six samples of the sandstones with trace amounts of Fe, Al, Ag, Na, K. The aqua regia digestion method was used to extract silicon and calcium from the rock samples in to synthesis the thin films. From (FT-IR), (SEM-EDS) and (XRD) we show that synthesis thin films at different temperture are composed mainly of 90.66 % calcite (CaCO3)/9.33 % α-quartz (SiO2) and 69 % α-quartz (SiO2)/31% Sodium Chloride (NaCl). The crystallite sizes of the sandstones were calculated and estimated to be nanometric, in contrast the thin films are not nanometric.

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This paper aims to numerical study of the experimental spectrum, in the context of the diagnosis of solid materials by spectroscopy; the resulting spectrum of fluorine plasma has beenanalyzed. The plasma is generated after the sublimation of the solid sample the fluorine by Laser Induced Breakdown Spectroscopy (LIBS technique). The theoretical spectra and the electronic temperature of a obtained plasma have been calculated, this temperature (1.92 eV) is well matched to the laboratory plasma criteria. The main results also are showed that the resulting medium consisted of 96.63% Calcium and 3.36% Fluor.