https://repositorio.ufu.br/handle/123456789/20564 2026-04-06T08:41:49Z https://repositorio.ufu.br/handle/123456789/48360 Title: O Efeito Bumerangue Quântico 2024-04-26T00:00:00Z https://repositorio.ufu.br/handle/123456789/47784 Title: Modelos efetivos e fatores giromagnéticos via DFT2kp e funcionais híbridos Abstract: The Density Functional Theory (DFT) and the k · p method are two important techniques for calculating the electronic band structures of crystalline materials, which is fundamental for studying their electronic, optical, and transport properties. The DFT2kp package inte- grates DFT and the k·p method by implementing computational routines for the automatic construction of effective k · p models from ab initio data generated by DFT calculations. In this work, we investigated how the hybrid functional Heyd–Scuseria–Ernzerhof 2006 (HSE06) influences the values of the parameters (effective mass, g-factors, and Dresselhaus constant) extracted from effective k · p models for GaAs. To this end, DFT calculations were performed using both the semilocal Perdew–Burke–Ernzerhof Generalized Gradient Approximation (PBE-GGA) functional and the hybrid HSE06 functional in various config- urations. The results show that the HSE06 functional yields band gaps and k · p model parameters that are more accurate than those obtained with the semilocal functional. It was also observed that these parameters are sensitive to adjustments of the tunable HSE06 parameters. Finally, an analysis of the variation of the k · p parameters as a function of the band gap was carried out, demonstrating that applying a scissor-shift to PBE-GGA calculations can produce results similar to those obtained with HSE06, suggesting that in applications tolerating some inaccuracy, the high computational cost of HSE06 may not be justified. 2025-09-23T00:00:00Z https://repositorio.ufu.br/handle/123456789/46704 Title: Himália: Determinação da órbita do maior satélite irregular de Júpiter Abstract: This work presents a study focused on improving the orbital determination of Himália, the largest irregular satellite of Jupiter, through numerical integrations and statistical analysis of observational data collected between 1886 and 2022. The adopted approach initially considers equal weights for all observations, aiming to identify discrepancies and prepare the dataset for more refined future processing. The application of the initial part of this methodology resulted in a consistent preliminary orbit, with potential to enhance future predictions. The results demonstrate that careful selection and differentiated statistical treatment of the observations positively impact orbital accuracy, highlighting the effectiveness of the developed method. 2025-05-22T00:00:00Z https://repositorio.ufu.br/handle/123456789/46287 Title: Estudo de estruturas perovskitas do tipo ABO3 através de simulações de dinâmica molecular Abstract: Technological advancements in computing, as well as improvements in program algorithms within the scope of computational physics, have enabled the application of computational simulations that drive the discovery and analysis of materials. Among the most significant computational advances is the Molecular Dynamics (MD) simulation method, where the structure and behavior of materials under different thermodynamic conditions can be investigated. In the last decade, perovskite-type ceramics have been intensely studied for being promising materials for the fabrication of photovoltaic cells. In addition to their application in solar energy, they have also stood out in the generation of other cleaner energies, such as SOFC-type fuel cells (Solid Oxide Fuel Cell). Silver niobate perovskite (AgNbO3), on the other hand, stands out for its use as a piezoelectric material in various electronic devices, such as capacitors and medical ultrasound tomography. In this work, we seek to explore Molecular Dynamics simulations as a tool to analyze structural, mechanical, and thermal properties of ABO3-type perovskite structures. We focused on different symmetries of silver niobate perovskite (AgNbO3), for which we obtained values comparable to reference values for structural properties such as volume and lattice parameters. We performed the analysis of the radial and angular distribution function, as well as the calculation of the bulk modulus and thermal expansion coefficient. For this, the force field was defined to reproduce the structure by using the Buckingham+Coulomb potential together with the core-shell model. Finally, we also sought to identify crystalline phase transitions and the melting point of the material, but without success. Thus, this work aims to highlight the limitations of the adopted model in not reproducing the structural distortions due to polarization effects and the mixed nature of the bonds present in the material, since it was not possible to adequately reproduce the studied structure. 2025-05-09T00:00:00Z