Speaker: Dr. Jorge Botana Alcalde
Applied Physics, University of Santiago de Compostela
Beijing Computational Science Research Center

Abstract: First, we studied ultrathin trilayers of Fen/Cr3/Fen (n = 1à6), in search of patterns in the properties of the trilayer as the thickness of the Fe layers grows. What we found is that the central layer of the Cr atoms absorbs electrons from the Fe ones. The extra electrons act as a perturbation that spreads a Friedel-like oscillation in the excess-defect of charge of the rest of the trilayer.

In the second topic, we calculated the properties of gold clusters in various situations. We showed that the 8-atom cluster remain 2D the structure distortions in 3D clusters causes the electron localization. We also found the 8-atom gold structures depend on their magnetic state. Furthermore, we searched the lowest energy configurations for AunO2 (n = 3à7) oxidized clusters and found that the biding of O2 with the cluster strongly depends on the number of Au atoms.

In another topic, we studied a transition metal alloy cluster, the Bi4Mn, which shows a disagreement between the measured magnetic moment and the values calculated by first principles method. After extensive exploration of all theoretical possibilities, we found none of the low energy structures of the Bi4Mn could possess magnetic moment that fits the experiment. Instead, we found the same magnetic moments exist in some high-energy isomers. As these isomers are very similar in structure to the Bi3Mn ones, we speculate that they could be the ones actually measured in the experiment.

The last part of the work includes the calculation of the optical properties of nanoparticles of thousands of Au atoms. We used the discrete dipole approximation to obtain the theoretical spectra of the nanoparticles in aqueous medium, in order to address the solution effects that are important in the experiments.

Date&Time: July 20, 2012  10:30 - 11:30
Location: 606 Conference Room