Renan Augusto Pontes Ribeiro

By Sergio Ricardo de Lazaro, Renan Augusto Pontes Ribeiro and Luis Henrique da Silveira Lacerda

Heterogeneous catalysis is a topic very studied in science. Its application in technologies of energy conversion, water purification, chemical synthesis, car catalytic converter and so on is studied. Recently, the TiO2 material in anatase and rutile phases has been used extensively in photocatalytic systems; its band-gap is localized in visible and ultra-violet spectra, proportioning a good material for generation of chemical radicals. Nowadays, the density functional theory (DFT) is shown as a great tool to simulate all types of materials and the possibilities to simulate bulk and surfaces of materials importance in last few decades. Recently, quantum periodic calculations based on DFT methods have been widely used to simulate materials and the main functionals applied are PBE, PBE0 and B3LYP; they are important for doping and adsorption theoretical investigations and are present in various simulation programs, such as, Crystal, Wien, Vasp and others. This methodology has investigate the influence of dangling bonds, cationic and anionic doping, charge transfer, surface energy and more quantum properties. Quantum chemistry tools, in particular, DFT methods, are key points to develop high quality research and technology once theoretical calculations are important to guide and understand the molecular design in photocatalysis.

Part of the book: Titanium Dioxide

By Sergio Ricardo De Lazaro, Luis Henrique Da Silveira Lacerda and Renan Augusto Pontes Ribeiro

In the last few years, the multiferroic materials have represented a very important research topic on the design of new technological devices. A better description for this kind of materials involves two or more forms of ferroic orders coupled in a single crystalline structure. The great number of studies in this field is focused on candidates that present the coupling between a magnetic order and ferroelectricity. However, these material classes are a challenging topic on first-principles calculations due to the strong correlation that arose from the unpaired electrons. Furthermore, the partial filling of d or f orbitals reduces a high localization and a strong interaction causing failures on the electronic structure prediction. The investigation of multiferroic materials aims at their application on the development of devices such as actuators, magnetic readers, sensors and data storage. Multiferroic materials are also alternatives to the production of technological applications based on spintronic. Our proposal is to show our experience in DFT simulations for magnetic states applied in oxides of ilmenites and corundum-ordered structures. Theoretical results reported for our group until now showed a good agreement with experimental results for half-metallicity, reduced band-gap, and/or ferromagnetic ordering.

Part of the book: Density Functional Theory