MODELAGEM ATOMÍSTICA CLÁSSICA DE PROPRIEDADES FÍSICAS E TRANSIÇÕES DE FASE ESTRUTURAIS EM MONOCRISTAIS

Neste trabalho foi apresentada uma breve revisão sobre a aplicação da modelagem atomística clássica na predição de transições de fase, no cálculo de observáveis físicos e do cálculo de defeitos. Também, uma breve discussão acerca da teoria envolvendo o método é apresentada.Palavras-chave: Simulação atomística. Potenciais interatômicos. Modelos iônicos. Interações.CLASSIC ATOMISTIC MODELING OF PHYSICAL PROPERTIES AND STRUCTURAL PHASE TRANSITIONS IN MONOCRYSTALSAbstract: In this work was presented a brief review on the application of classical atomistic modeling to predict phase transitions, calculate physical observables and the defects modeling. Also, a brief discussion of the theory involving the method is presented. Keywords: Atomistic simulation. Interomic potentials. Ionic models. Interactions.MODELADO ATOMÍSTICO CLÁSICO DE PROPIEDADES FÍSICAS Y DE TRANSICIONES DE FASE ESTRUCTURALES EN MONOCRISTALESResumen: Este trabajo se presentó una breve reseña sobre la aplicación del modelo atomistaclásica para predecir las transiciones de fase, en el cálculo de los observables físicos y el cálculo de los defectos. Además, una breve discusión sobre la teoría que rodea el método se presenta.Palabras clave: Simulación atomística. Potenciales interatómicos. Modelos de orden jónico. Interacciones

Concentration of Charge Carriers, Migration, and Stability in Li₃OCl Solid Electrolytes

Recently, a new family of lithium-rich antiperovskites, Li₃OA (A = halogen), which presents superionic conductivity, emerged as a promising both safe and commercially applicable solid electrolyte for lithium ion batteries. In this paper we employed classical atomistic quasi-static calculations to obtain the concentration of lithium vacancies and interstitials for stoichiometric samples of Li₃OCl. The obtained concentrations as well as vacancy and interstitial migration energies reinforced the assumption that vacancies are the charge carriers in both stoichiometric and divalent metal doped samples, but raise the possibility that the high ionic conductivity in LiCl-deficient samples are in fact driven by interstitials, in opposition to what has been assumed so far. The Li₃OCl stability at higher temperatures was investigated based on Gibbs energies of decomposition from 0 K up to 550 K. They are negative in the whole temperature range, which suggests that there exists a high Gibbs energy barrier between Li₃OCl and starter materials preventing decomposition

Facile Gram-Scale Synthesis of NiO Nanoflowers for Highly Selective and Sensitive Electrocatalytic Detection of Hydrazine

The design and development of efficient and electrocatalytic sensitive nickel oxide nanomaterials have attracted attention as they are considered cost-effective, stable, and abundant electrocatalytic sensors. However, although innumerable electrocatalysts have been reported, their large-scale production with the same activity and sensitivity remains challenging. In this study, we report a simple protocol for the gram-scale synthesis of uniform NiO nanoflowers (approximately 1.75 g) via a hydrothermal method for highly selective and sensitive electrocatalytic detection of hydrazine. The resultant material was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. For the production of the modified electrode, NiO nanoflowers were dispersed in Nafion and drop-cast onto the surface of a glassy carbon electrode (NiO NF/GCE). By cyclic voltammetry, it was possible to observe the excellent performance of the modified electrode toward hydrazine oxidation in alkaline media, providing an oxidation overpotential of only +0.08 V vs Ag/AgCl. In these conditions, the peak current response increased linearly with hydrazine concentration ranging from 0.99 to 98.13 μmol L–1. The electrocatalytic sensor showed a high sensitivity value of 0.10866 μA L μmol–1. The limits of detection and quantification were 0.026 and 0.0898 μmol L–1, respectively. Considering these results, NiO nanoflowers can be regarded as promising surfaces for the electrochemical determination of hydrazine, providing interesting features to explore in the electrocatalytic sensor field