2 research outputs found
Ground state structural, lattice dynamic, thermodynamic and optical properties of the Ba₂CaMoO₆ ordered perovskite
Ab-initio calculations based on density functional theory have been performed to establish the ground state properties for the double perovskite type material Ba₂CaMoO₆. The calculations were carried out through the Projector Augmented Wave Method and the exchange and correlation was described using the Perdew-Burke- Ernzerhof parameterization of the Generalized Gradient Approximation. The study included structural analysis of the material, as well as thermodynamic, cell dynamics and optical properties at its transition between the tetragonal I4/m and cubic Fm 3 m phases. The results on the structural stability reveal that the phase with space group of I4/m is more stable. Likewise, the structural phase transition was obtained for a pressure of 0.067 GPa.
On the other hand, the analysis of the electronic properties shows that the material presents a semiconducting behaviour, with a direct band gap of 2.40 eV and 2.26 eV for the tetragonal and cubic structures, respectively. In addition to agreeing with the experimental values reported in the literature, the results suggest possibilities for the application of this material in photodetectors, light emitters and devices for power electronics.Instituto de FÃsica La Plat
Naturaleza electrónica espÃn-metálica y propiedades termofÃsicas del molibdato de cobalto tipo perovskita Baâ‚‚CoMoO₆
Perovskite-like materials which include magnetic elements have relevance due to the technological perspectives in the spintronics industry. In this work, the magnetic, structural and electronic properties of the Baâ‚‚CoMoO₆ double perovskite are investigated. Calculations are carried out through the Full-Potential Linear Augmented Plane Wave method within the framework of the Density Functional Theory with exchange and correlation effects in the Generalized Gradient and Local Density approximations, including spin polarization. From the minimization of energy as a function of volume using Murnaghan’s state equation the equilibrium lattice parameter and cohesive properties of this compound were obtained. The study of the electronic structure was based in the analysis of the electronic density of states, and the band structure, showing that this compound evidences a conductive character for a spin channel and insulation for the other, and presents an integer value for the effective magnetic moment (3.0 μB), which allows it to be classified as a half-metallic material. The effects of pressure and temperature on thermophysical properties such as specific heat, Debye temperature, coefficient of thermal expansion and the Grüneisen parameter were calculated and analyzed from the state equation of the system. Obtained results reveal that, in the low-temperature regime, the specific heat at constant volume and pressure presents an analogous behavior to each other, with a tendency to the limit of Dulong-Petit typical of the structures of cubic perovskite-type, showing a value of 246.3 J/mol.K at constant volume and slightly higher values at constant pressure. The dependence of the thermal expansion coefficient, the temperature of Debye and the Grüneisen parameter with the increase in temperature are discussed in relation to other perovskite-like materials.Los materiales de tipo perovskita que incluyen elementos magnéticos tienen relevancia debido a las perspectivas tecnológicas en la industria de la espintrónica. En este trabajo se efectúa un estudio exhaustivo de las propiedades magnéticas, estructurales y electrónicas de la perovskita doble Baâ‚‚CoMoO₆. Los cálculos se realizan a través del método de ondas planas aumentadas y linealizadas dentro del marco de la teorÃa del funcional de la densidad con efectos de intercambio y correlación en las aproximaciones del gradiente generalizado y de densidad local, incluyendo polarización de espÃn. A partir de la minimización de la energÃa en función del volumen, utilizando la ecuación de estado de Murnaghan, se obtuvieron el parámetro de red de equilibrio y las propiedades cohesivas de este compuesto. El estudio de la estructura electrónica se basó en el análisis de la densidad electrónica de estados y la estructura de bandas, mostrando que este compuesto evidencia un carácter conductor para un canal de espÃn y aislante para el otro, presentando un valor entero para el momento magnético efectivo (3.0 μB), que permite clasificarlo como un material espÃn-metálico. Los efectos de la presión y la temperatura sobre las propiedades termofÃsicas, como el calor especÃfico, la temperatura de Debye, el coeficiente de expansión térmica y el parámetro Grüneisen, se calcularon y analizaron a partir de la ecuación de estado del sistema. Los resultados obtenidos revelan que, en el régimen de baja temperatura, el calor especÃfico a volumen y presión constantes presenta un comportamiento análogo entre sÃ, con una tendencia al lÃmite de Dulong-Petit tÃpico de las estructuras de tipo perovskita cúbica, mostrando un valor de 246.3 J/mol.K a volumen constante y valores ligeramente más altos a presión constante. La dependencia del coeficiente de expansión térmica, la temperatura de Debye y el parámetro Grüneisen con el aumento de temperatura se discute en relación con otros materiales de tipo perovskita.Instituto de FÃsica La PlataGrupo de Estudio de Materiales y Dispositivos Electrónico