| 1. |
- Escamilla-Roa, Elizabeth, et al.
(författare)
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DFT study of electronic and redox properties of TiO2 supported on olivine for modelling regolith on Moon and Mars conditions
- 2020
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 180
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide TiO2 is one of the most studied oxides in photocatalysis, due to its electronic structure and its wide variety of applications, such as gas sensors and biomaterials, and especially in methane-reforming catalysis. Titanium dioxide and olivine have been detected both on Mars and our Moon. It has been postulated that on Mars photocatalytic processes may be relevant for atmospheric methane fluctuation, radicals and perchlorate productions etc. However, to date no investigation has been devoted to modelling the properties of TiO2 adsorbed on olivine surface.The goal of this study is to investigate at atomic level with electronic structure calculations based on the Density Functional Theory (DFT), the atomic interactions that take place during the adsorption processes for formation of a TiO regolith. This model is formed with different TiO films adsorbed on olivine (forsterite) surfaces, one of the most common minerals in Universe, Earth, Mars, cometary and interstellar dust. We propose three regolith models to simulate the principal phase of titanium oxide (TiO, Ti2O3 and TiO2). The models show different adsorption processes i.e. physisorption and chemisorption. Our results suggest that the TiO is the most reactive phase and produces a strong exothermic effect. Besides, we have detailed, from a theoretical point of view, the effect that has the adsorption process in the electronic properties such as electronic density of state (DOS) and oxide reduction process (redox). This theoretical study can be important to understand the formation of new materials (supports) that can be used as support in the catalytic processes that occur in the Earth, Mars and Moon. Also, it may be important to interpret the present day photochemistry and interaction of regolith and airborne aerosols in the atmosphere on Mars or to define possible catalytic reactions of the volatiles captured on the Moon regolith.
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| 3. |
- Hernández-Laguna, Alfonso, et al.
(författare)
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Compressibility of 2M1 muscovite-phlogopite series minerals
- 2019
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Ingår i: Journal of Molecular Modeling. - : Springer. - 1610-2940 .- 0948-5023. ; 25:11
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Tidskriftsartikel (refereegranskat)abstract
- Muscovite (Ms) and phlogopite (Phl) belong to the 2:1 dioctahedral and trioctahedral layer silicates, respectively, and are the end members of Ms-Phl series minerals. This series was studied in the 2M1 polytype and modeled by the substitution of three Mg2+ cations in the Phl octahedral sites by two Al3+ and one vacancy, increasing the substitution up to reach the Ms. The series was computationally examined at DFT level as a function of pressure to 9 GPa. Cell parameters as a function of pressure and composition, and bulk moduli as a function of the composition agrees with the existing experimental results. The mixing Gibbs free energy was calculated as a function of composition. From these data, approximated solvi were calculated at increasing pressure. A gap of solubility is found, decreasing the gap of solubility at high pressure.
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