Skip Ribbon Commands
Skip to main content
Sort by AttachmentsUse SHIFT+ENTER to open the menu (new window).
The theme of this research is to predict the magnetic structure of different structures from first principles using the state-of-the art density functional theory to tackle the many-body problem in solving Schroedinger's equation for solids. One branch of this research is the magnetic and electronic properties of transition metal surfaces and interfaces. The exciting aspects of such low-dimensional systems are the discovery of unexpected magnetic behavior at surfaces and ultra-thin films such as the magnetocrystalline anisotropy. The interlayer exchange coupling is also investigated in superlattice structures composed of ferromagnetic materials mediated by non-magnetic spacers such as Con/Irm, Fen/Irm and Fen/Wm superlattices. In addition, the magnetic structure is investigated in Mn-based binary alloys of CuAu-I type structure that exhibit a change in the magnetic structure due to volume change such as MnPd that has an antiferromagnetic state, which changes to ferromagnetic for the CsCl-type structure. The fact that makes MnRh prospective as a giant magnetostrictive material.
In this branch, the oxidation of carbon monoxide is investigated using transition-metal catalytic surfaces. The study of CO oxidation reaction is of practical importance for the control of the environmental pollution that results from combustion processes. In general, the catalytic activity for the CO oxidation over transition metal surfaces is determined by the propensity of the metal surface to dissociate oxygen molecules and counter balanced by the bond strength of the active oxygen species on the metal surface. We analyze the adsorption of O and CO on transition metal surfaces such as Ir(100) using the electronic structure interpretations to provide a deep understanding of the site preference for different coverages. The pathway and transition state are then determined using constrained minimization and nudge elastic band methods. The key event of such reactions is the movement of both CO and O to a site with less stability. The energy barrier is then determined, which is the energy needed for the diffusion of the species to activated sites and weakening for species bonds with metal surface.
Thermoelectric (TE) materials are solid state devices that could be designed using two dissimilar materials such as n-and p-type semiconductors, connected electrically in series and thermally in parallel. Thermoelectric devices are double functional devices that can be used for power generation or refrigeration. They can be designed to convert thermal energy from a temperature gradient into electrical energy (Seebeck effect), where carriers diffuse from the hot to the cold side creating a voltage drop and a current flow. However, if a voltage drop is applied to the TE ends, a current flows from one end carrying heat to the other creating a temperature gradient (Peltier effect). Te-based alloys are known to have the highest figure-of-merit (ZT) value, which is a measure of TE performance. However, these materials are not very promising for functional applications due to their high costs, low natural abundance, instability at high temperatures, and toxicity. Therefore, oxides appear to be a better alternative as they are of low cost, more abundance and stable against decomposition at high temperatures, the fact that makes them more appropriate for applications, specially in power generation. In this branch of research, we calculate the transport properties (Seebeck coefficient, electrical and thermal conductivities) of tungsten bronze oxides to predict materials of high figure-of-merit.