چكيده لاتين
Density functional theory (DFT) is a powerful tool in the world of condensed matter physics and computational chemistry that has opened a new window to a deeper understanding of the electronic properties of materials. This theory is based on the fundamental idea that all the electronic properties of a system can be extracted and predicted by having its charge density. The widespread applications of DFT, from calculations of crystal structures and thermodynamic predictions to the band structure calculations, phonon and other properties show the ability and efficiency of this theory in the study of materials. In recent years, the DFT role in the finding and studying of topological phases has opened a new window to the fascinating world of materials with extraordinary properties. Topological insulators are one of the most prominent examples of topological materials. These materials are insulating in their bulk, while exhibit electrical conductivity channels on their surface or boundaries. This phenomenon is due to the presence of surface or edge states with specific topological properties, in which spin-orbit interaction plays a fundamental role. Dirac and Weyl topological semimetals are other fascinating examples of this class of materials. These materials, respectively, have Dirac points and Weyl nodes in their band structure, which grant them unique transport properties. The breaking of either time-reversal or spatial inversion symmetry plays a crucial role in realizing such topological phases. The presence of surface states called Fermi arcs is one of the most striking features of these materials. Studies show that by applying external factors such as pressure, strain, doping and alloying, electric field, etc., can create topological phases or different topological classes in materials. This opens up new avenues for the design and fabrication of materials with advanced properties in various fields of science and technology, including spintronics, superconductivity, and quantum computing.
This thesis aims are to search for topological phases and classes in proposed compounds using the ability of DFT. In this research, the role of factors such as hydrostatic pressure, uniaxial stress and strain, and doping with different concentrations on the topological phase transitions of some materials will be investigated. The study, calculation and analysis of topological properties such as topological invariants, band order (normal and inversion bands), and topological surface states are among the key objectives of this research. In addition, the physical, mechanical properties and stability conditions of the compounds will also be investigated. This thesis is expected to lead to the introduction and finding of new materials with topological phases and a deeper understanding of the mechanisms of topological phase transitions. The findings of this research can be an important step towards the development of topological materials science and its applications in various fields.
