Estudio de las propiedades electrónicas de cúmulos de Pd: un estudio comparativo usando distintas técnicas y aproximaciones

Abstract

A systematic study of the colineal and no-colineal magnetic properties and the metallic behavior in free standing clusters of Pd$_N$ ($2{\le} N{\le} 21$) is carried out. We also study the effect of the twinning in clusters on the magnetism in clusters up to $N=116$ atoms. To this aim we use two techniques: in one hand the ab initio based on the density functional theory (DFT) and on another hand semi-empirical based on the tight binding (TB) Hamiltonian. These are two of the most common used techniques to study the electronic properties of clusters. We found that the colineal magnetism has a no-monotonic decreasing behavior as a function of the cluster size. We observe that the twinning of clusters in some cases can increase the magnetic moment of relatively large size clusters. We found that the no-colineal magnetism always corresponds to a low energy excited state, and that the ground state always presents a colineal magnetic order. Respect to the methods, in general we found that the semi-empirical ones describe very well the electronic properties, as the magnetism; that are obtained from the difference between electronic populations. Although the metallicity requires of the exact determination of the position of the electronic states, it is razonably described by the semi-empirical method if the clusters size is big enough. We compare our results with previous calculations as well as with some experiments reported in the literature.