Compressional behavior of the aragonite-structure carbonates to 6 GPa

Supplementary Information The online version contains supplemen- tary material available at https://doi.org/10.1007/s00269-023-01237-6.The behaviors of aragonite (CaCO3 ), strontianite (SrCO3 ), cerussite (PbCO3 ), and witherite (BaCO3 ) at increasing pressure have been studied up to 6 GPa using density functional theory with plane waves. A parallelism of the orthorhombic carbonates with the closed-packed AsNi structure is considered in our analysis, being the CO2−3 groups not centered in the interstice of the octahedron. The decomposition of the unit-cell volume into atomic contributions using the Quantum Theory of Atoms in Molecules has allowed the analysis of the bulk modulus in atomic contributions. The bulk, axes, interatomic distances, and atomic compressibilities are calculated. The largest compression is on the c crystallographic axis, and the c linear modulus has a linear function with the mineral bulk modulus (K0 ). Many of the interatomic distances moduli of the alkaline earth (AE) carbonates show linear functions with the bulk modulus; however, the whole series (including cerussite) only gives linear functions when K0 is related either with the CC distances modulus or the modulus of the distances of the C to the faces of the octahedron perpendicular to c. These last distances are the projections of the Metal–Oxygen (MO) distances to the center of the octahedron. K0AE carbonates also show linear functions with the atomic moduli of their cations. However, the whole series show a linear relation with the atomic modulus of C atoms. Therefore, the whole series highlight the importance of the C atoms and their interactions in the mechanism of compression of the orthorhombic carbonate series.Spanish MCINN and European FEDER Grants FIS2016-77692-C2. 2PCIN-2017-098Junta de Andalucía for the RNM-264-363 and RNM-264-1897 PAI-Grant

2M1 phlogopite–muscovite series minerals at increasing pressure to 9 GPa. I Atomic volumes and compressibilities

Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Authors are thankful to Andalusian project P18-RT-3786 for financial support, and to the Computational Centers of the University of Granada and CSIC for computational facilities.Muscovite (Ms) and phlogopite (Phl) series mineral is studied in the 2M1 polytype and modeled by the substitution of three Mg2+ cations in the three octahedral sites of Phl [KMg3(Si3Al)O10(OH)2] by two Al3+ and one vacancy, increasing the substitution up to reach the Ms [KAl2□(Si3Al)O10(OH)2]. The series was computationally examined at DFT using Quantum ESPRESSO, as a function of pressure from − 3 to 9 GPa. Crystal structure is calculated, and cell parameters, and geometry of atomic groups agree with experimental values. OH in the Mg2+ octahedrons are approximately perpendicular to the (001) plane, meanwhile when they are in Al3+, octahedral groups are approximately parallel to this plane. From Quantum Theory of Atoms in Molecules, the atomic basins are calculated as a function of the pressure, K+ and basal O show the largest volumes. The bulk excess volume (Vxs) and the excess atomic volumes are analyzed as a function of the composition and the pressure. K+, basal and apical O Vxs show a behavior similar to the bulk Vxs as a function of the composition, keeping qualitatively this behavior as a function of pressure; substituent atoms do not show a Vxs behavior similar to the bulk and their effect consequently is mostly translated to atoms in the interlayer space. Atomic compressibilities are also calculated. Atomic compressibilities are separated in the different sheets of the crystal cell. Atomic moduli of K and basal O are the lowest and the ones behaving as the bulk modulus of the series. The atomic bulk modulus of the H’s is different depending of their position with respect to the (001) plane.CRUE-CSICAndalusian project P18-RT-378

Understanding the role of nitrogen-doping and surface topology in the binding of Fe(III)/Fe(II) to biobased carbon electrodes

Low-cost and high performance electrodes are critical to advance electrochemical energy storage devices that decouple energy supply from demand. At their core, carbon is ubiquitously employed given its availability, chemical and electrochemical stability, electrical conductivity, and affordable cost. However, due to their relative inertness, carbonaceous electrodes suffer from limited wettability and kinetic activity with aqueous electrolytes. A common approach is to introduce heteroatoms, either through post-processing (thermal/acid activation) or by employing different precursors. Specifically, biobased carbons like hydrochar and biochar are rich in heteroatoms that are naturally incorporated through the production process into the electrode structure. However, achieving a fundamental understanding of the interactions between metal ions and carbon surfaces has proven elusive, leading researchers to rely on empirical approaches for heteroatom doping of carbons. To achieve a better understanding of the fundamental mechanisms, we performed density functional theory calculations of a commonly employed iron redox couple, Fe(III) and Fe(II). We investigated binding mechanisms in graphitic carbon model systems with different surface features, and explored the effect of nitrogen doping and surface topology on the binding energy, as well as the effect of ions’ spin multiplicity in the carbon-metal coordination mechanisms. Our results suggest that the interactions of Fe(III) and Fe(II) ions with the nitrogen-doped carbon electrodes not only depend on the surface curvature or the nitrogen content and functionality, but also on the spin multiplicity of the metal ion. Iron ions always evolve into an open-shell electronic structure with a high number of unpaired electrons to increase their coordination sphere with the graphitic surface. We hope that our findings can assist the development of fit-for-purpose heteroatom-doped carbon electrodes with a tailored nanostructure for electrochemical devices utilizing the Fe(III)/Fe(II) redox couple.</p

Estudio computacional sobre la naturaleza del enlace carbono-metal: análisis topológico QTAIM y ELF

Tesis Univ. Granada. Departamento de Química Orgánica. Leída el 18 de junio de 200

Smart Technologies. SmartTech-IC 2022: Third International Conference on Smart Technologies, Systems and Applications

La Universidad Politécnica Salesiana ha estado promoviendo la investigación científica proporcionando financiamiento para el desarrollo y ejecución de propuestas en diversas áreas de investigación. En la Sede Cuenca, se han formado grupos multidisciplinarios para llevar a cabo estas propuestas de investigación. Aunque estos indicadores demuestran resultados favorables en la implementación de una cultura de investigación sólida, todavía se informan proyectos que, debido a varios factores, no logran publicar sus resultados en revistas indexadas. Entre estos factores se encuentran los altos costos de movilidad de los investigadores para presentar sus trabajos en eventos indexados, así como la falta de implementación de criterios adecuados de cienciometría. Esto ha impedido que, en muchos casos, investigaciones con resultados sobresalientes no sean comunicadas a la comunidad científica internacional, lo que no contribuye al aumento de la productividad académica institucional. Además, en algunos casos, se publican trabajos en revistas sin una indexación que contribuya a los indicadores institucionales (Castillo y Powell, 2019) (Guerrero-Casado, 2017)