Characterization of the TiSiO4 structure and its pressure-induced phase transformations: density functional theory study

Theoretical investigations concerning the possible titanium silicate polymorphs have been performed using density functional theory at B3LYP level. Total-energy calculations and geometry optimizations have been carried out for all phases involved. The following sequence of pressure-driven structural transitions has been found: CrVO4 -type, Cmcm in parenthesis the transition pressure , → zircon-type, I41 / amd 0.8 GPa , → scheelite-type, I41 / a 3.8 GPa . At higher pressure the last phase is found to be stable at least up to 25 GPa. The equation of state of the different polymorphs is also reported. We found that the highest bulk modulus corresponds to the zircon and scheelite phases with values of 248 and 238 GPa, respectively. The orthorhombic Cmcm phase is the most compressible of all the studied structures with a bulk modulus of 124 GPa, being also the most stable phase at ambient pressure. Finally, calculations of the electronic structure, vibrational and dielectric properties of TiSiO4 are also reporte

Polymorphs of ZnV2O6 Under Pressure: a First Principle Investigation

This work presents first-principle calculations on the pressure-dependence of the stabilities, structures, and electronic properties of several polymorphs of ZnV2O6 under the pressure range 0-30 GPa. These properties are analyzed and discussed in detail using the different parameterizations of the exchange-correlation functional (B3LYP, HSE06, and PBE), and the results are compared with available experimental data. An extensive search process was carried out on the potential energy surface for a set of twelve possible polymorphs. Ten of them are stationary points, but only five have positive frequency values in the range of 0-30 GPa, i.e., monoclinic brannerite (C2/m and C2), orthorhombic columbite (Pbcn), trigonal CaAs2O6-type (P321), and triclinic NiV2O6-type (P1̅). The monoclinic ThTi2O6-type (C2/c) phase presents a very low imaginary frequency around 50 cm-1 . Orthorhombic SrV2O6-type and BaV2O6-type, tetragonal trirutile and trigonal PbSb2O6 -type structures show several imaginary negative frequencies between -400 and -100 cm-1 . These imaginary frequencies are indicative of structural instabilities. All attempts to try to converge the calculations to obtain the MoLa2O6-type and HgV2O6-type polymorphs, by using the three functionals, have been unsuccessful. For both brannerite,ThTi2O6-type, columbite, CaAs2O6-type, NiV2O6-type structures numerical and analytical fittings were performed to obtain the lattice parameters, the bulk modulus, B, and their pressure derivative, B′, and the energy-volume relationship of phases are analyzed. Vibrational calculations were performed at each pressure for each polymorph and compared with available experimental data

Identifying and explaining vibrational modes of sanbornite (low- BaSi2O5) and Ba5Si8O21: A joint experimental and theoretical study

We report here the analysis of vibrational properties of the sanbornite (low-BaSi2O5) and Ba5Si8O21 using theoretical and experimental approaches, as well as results of high temperature experiments up to 1100-1150 ̊C. The crystal parameters derived from Rietveld refinement and calculations show excellent agreement, within 4%, while the absolute mean difference between the theoretical and experimental results for the IR and Raman vibrational frequencies was <6 cm -1. The temperature-dependent Raman study renders that both sanbornite and Ba5Si8O21 display21 specific Ba and Si sites and their Ba-O and Si-O bonds. In the case of the stretching modes assigned to specific Si sites, the frequency dependence on the Si-O bond length exhibited very strong correlations. Both phases showed that for a change of 0.01 Å, the vibrational mode shifted 10 ± 2 cm-1. These results are promising for using Raman spectroscopy to track in situ reactions under a wide variety of conditions, especially during crystallization

Laboratori de Química Física II

El document forma part dels materials docents programats mitjançant l'ajut del Servei de Política Lingüística de la Universitat de ValènciaEl “Laboratori de química física II” és una assignatura obligatòria que s’imparteix en el segon quatrimestre durant el tercer curs del grau en Química. És un laboratori que fa èmfasi en l’experimentació en termodinàmica química d’interfases, espectroscòpia, electroquímica, fotoquímica, química quàntica i cinètica química. En el laboratori s’apliquen diverses tècniques instrumentals a l’estudi de sistemes d’interès quimicofísic i s’utilitzen ordinadors per a l’estudi d’àtoms i molècules

Diagnóstico del manejo de los residuos sólidos orgánicos generados en el municipio de Mitú- Vaupés.

Anexo A. Ficha técnica de la encuesta, Anexo B. Resultados tabulados de las encuestasEl municipio de Mitú es la capital del Departamento de Vaupés, se encuentra ubicado en el extremo sur oriental de Colombia, limitando con Brasil. El municipio cuenta con más de 16000 kilómetros cuadrados y cuenta con una población superior a los 30.000 habitantes. Lo que mueve principalmente la economía del municipio es el enclave administrativo y militar. El atraso que presenta el municipio no solo se observa en la parte económica, sino también en la prestación de los servicios públicos, especialmente en el correspondiente a la recolección de los residuos sólidos municipales; actualmente el municipio genera más de 50 Ton mensuales de residuos los cuales son dispuestos en un botadero a cielo abierto, sin tratamiento ni aprovechamiento alguno, a pesar que según el Plan de Desarrollo, el municipio cuenta con la infraestructura para un relleno sanitario, el cual hasta el momento no se ha puesto en marcha por falta de recursos financieros. De acuerdo al diagnóstico realizado en este proyecto, el cual se llevó a cabo a través de encuestas aplicadas a la comunidad, entrevistas realizadas a las entidades territoriales, y la observación directa, se identificó que en el municipio existen vacíos relacionados con el adecuado manejo de los residuos sólidos, incluso algunas zonas no cuentan con servicio de recolección por parte de la empresa de aseo y los habitantes recurren a prácticas como arrojarlos al río o quemarlos para poder deshacerse de ellos. El tipo de residuo que más se genera es el orgánico, representando más del 33% del total de los residuos, lo cual concuerda con las actividades que principalmente realiza su población; estos residuos no están siendo aprovechados de ninguna manera. En el municipio se evidencia la necesidad de contar con un mayor compromiso por parte de la administración local, en la ejecución de proyectos de sensibilización de la población, así mismo, por parte de la población es necesario la interiorización de la problemática y la realización de actividades que promuevan tanto la disminución en la generación de los residuos, como el adecuado aprovechamiento y disposición de los mismos.The municipality of Mitú is the capital of the Department of Vaupés, it is located in the extreme south east of Colombia, bordering Brazil. The municipality has more than 16,000 square kilometers and has a population of more than 30,000 inhabitants. What mainly moves the economy of the municipality is the administrative and military enclave. The delay presented by the municipality is not only observed in the economic part, but also in the provision of public services, especially in the corresponding to the collection of municipal solid waste; currently the municipality generates more than 50 tons of waste per month which are disposed of in an open dump, without any treatment or use, despite the fact that according to the Development Plan, the municipality has the infrastructure for a sanitary landfill, which So far it has not been launched due to lack of financial resources. According to the diagnosis made in this project, which was carried out through surveys applied to the community, interviews with territorial entities, and direct observation, it was identified that in the municipality there are gaps related to the adequate management of solid waste, even some areas do not have collection service by the cleaning company and the inhabitants resort to practices such as throwing them into the river or burning them to get rid of them. The most generated type of waste is organic, representing more than 33% of the total waste, which is consistent with the activities carried out mainly by its population; This waste is not being used in any way. In the municipality there is evidence of the need for greater commitment on the part of the local administration, in the execution of awareness projects for the population, and on the part of the population, the internalization of the problem and the realization of activities that promote both the decrease in the generation of waste, and the proper use and disposal of them

Effects of surface stability on the morphological transformation of metals and metal oxides as investigated by first-principles calculations

Morphology is a key property of materials. Owing to their precise structure and morphology, crystals and nanocrystals provide excellent model systems for joint experimental and theoretical investigations into surface-related properties. Faceted polyhedral crystals and nanocrystals expose well-defined crystallographic planes depending on the synthesis method, which allow for thoughtful investigations into structure-reactivity relationships under practical conditions. This feature article introduces recent work, based on the combined use of experimental findings and first-principles calculations, to provide deeper knowledge of the electronic, structural, and energetic properties controlling the morphology and the transformation mechanisms of different metals and metal oxides: Ag, anatase TiO2, BaZrO3, and α-Ag2WO4. According to the Wulff theorem, the equilibrium shapes of these systems are obtained from the values of their respective surface energies. These investigations are useful to gain further understanding of how to achieve morphological control of complex three-dimensional crystals by tuning the ratio of the surface energy values of the different facets. This strategy allows the prediction of possible morphologies for a crystal and/or nanocrystal by controlling the relative values of surface energies.The authors are grateful to FAPESP (2013/07296-2, 2012/ 14468-1, 2013/26671-9 and 2014/04350-9), CAPES (process A104/2013 and 99999.002998/2014-09), CNPq INCTMN 573636/2008-7, PrometeoII/2014/022 and ACOMP/2014/270 projects (Generalitat Valenciana), Ministerio de Economia y Competitividad (Spain), CTQ2012- 36253-C03-02 and the Spanish Brazilian program (PHB2009-0065-PC) for financially supporting this research. We also acknowledge the Servei Informática, Universitat Jaume I for a generous allotment of computer time

CORRESPONDENCE BETWEEN PERSONALITY AND JOB TITLE

Does the position held by an individual in a company fit into his/her personality? The answer to this question is yes. This is because there is significant relationship between the characteristics possessed by a worker which includes his character, personality and way of life, with the current position he/she is holding in an organization. The evolution of man is in accordance with technological advancement, new cultures, social and economic developments, among other phenomena. In other words, the success in the position given to a person will depend largely on his/her personality from a mental and physical point of view. This aim of this paper is to analyze the part of clinical psychology which is associated with human talent through a series of characteristics and personality traits. Personality traits and characteristics are crucial for the proper performance of a worker in a specific job

A 3D platform for the morphology modulation of materials: first principles calculations on the thermodynamic stability and surface structure of metal oxides: Co3O4, α-Fe2O3, and In2O3

Essentially, the exposed crystal planes of a given material, which primarily determine their morphology, tremendously affect its behavior. First principle calculations, based on the Wulff construction model and broken bonding density index, have been performed to calculate the equilibrium and their transformations for different metal oxides: Co3O4, α-Fe2O3, and In2O3. Present results point out that starting by surface thermodynamics is a helpful approach to predict and assess the morphology transformations of these materials. These complete set of morphologies may serve as a guide for researchers, when analyzing the images from electron microscopies, to gain further understanding of how to control crystal shape synthetically by tuning the surface chemistry and by controlling the relative values of surface energies

Validación de un instrumento de medición que analiza la cultura organizacional desde dos perspectivas

La cultura organizacional se entiende como el conjunto de creencias y significados que han sido naturalizados por los miembros de la organización en el marco de un orden hegemónico, convirtiéndose en simbolismo de interpretación, orientador de conductas y prácticas. Con este enfoque, el presente estudio se interesa en validar un instrumento de medición que permite analizar la cultura organizacional desde dos perspectivas: la real e ideal, y reconocer cómo las personas que laboran en una organización entienden e interpretan su experiencia y cómo se conectan en su entorno, es decir, con la comunicación existente, los conflictos, la creatividad, cómo los discursos y prácticas que circulan en la organización están inmersos en relaciones de poder y por supuesto, en la lucha por el control, por lo que se realiza una validez de criterio al correlacionar las puntuaciones de los participantes obteniendo una correlación positiva cercana a la media. En una primera aproximación se comprueba, para 35 casos de estudio, que existe una asociación positiva entre las culturas ideal y real percibida por los integrantes de la organización, posteriormente, y con miras hacia una cultura óptima o necesaria, se hace uso de la distancia de Hamming la que permitió visualizar una mayor apreciación en la administración de conflictos y una menor apreciación para la planeación. Conocer esta relación es fundamental, ya que a partir de la determinación del gap o brecha existente entre ambas culturas se podrán plantear acciones para cerrarla

Intercalation processes and diffusion paths of lithium ions in spinel-type structured Li1+xTi2O4: density functional theory study

Intercalation processes and corresponding diffusion paths of Li ions into spinel-type structured Li1+xTi2O4 0 x 0.375 are systematically studied by means of periodic density functional theory calculations for different compositions and arrangements. An analysis of the site preference for intercalation processes is carried out, while energy barriers for the diffusion paths have been computed in detail. Our results indicate that the Li insertion is thermodynamically favorable at octahedral sites 16c in the studied composition range, and Li migration from tetrahedral sites 8a to octahedral sites 16c stabilizes the structure and becomes favorable for compositions x 0.25. Diffusion paths from less stable arrangements involving Li migrations between tetrahedral and octahedral sites exhibit the lowest energy barrier since the corresponding trajectories and energy profiles take place across a triangle made by three neighboring oxygen anions without structural modification. Theoretical and experimental diffusion coefficients are in reasonable agreemen