Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1798781 | Journal of Magnetism and Magnetic Materials | 2016 | 15 Pages |
Abstract
We present first-principles theoretical calculations of the magnetic properties of bimetallic clusters Ag-Cu. The calculations proceeded by combining a previously developed state-of-the-art optimization algorithm (P.J. Hsu, S.K. Lai, J. Chem. Phys. 124 (2006) 0447110) with an empirical potential and applied this numerical scheme to determine first the lowest energy structures of pure clusters Ag38 and Cu38, and also their different atomic compositions AgnCu38ân for n=1,2,â¦,37. Then, we carried out the Kohn-Sham spin unrestricted density functional theory calculations on the optimized atomic structures obtained in the preceding step. Given the minimized structures from the first step as input configurations, the results of these re-optimized structures by full density functional theory calculations yield more refined electronic and atomic structures. A thorough comparison of the structural differences between these two sets of atomic geometries, one from using an empirical potential in which the electronic degrees of freedom were included approximately and another from subsequent minimization using the spin unrestricted density functional theory, sheds light on how the electronic charges disperse near atoms in clusters AgnCu38ân, and hence the distributions of electronic spin and charge densities at re-optimized sites of the cluster. These data of the electronic dispersion and the ionic configuration give clue to the mystery of the unexpected net magnetic moments which were found in some of the clusters AgnCu38ân at n=1-4, 24 as well as the two pure clusters. Possible origins for this unanticipated magnetism were explained in the context of the point group theory in much the same idea as the Clemenger-Nilsson model applied to simple metal clusters except that we draw particular attention to the atomic topologies and stress the bearing that they have on valence electrons in inducing them to disperse and occupy different molecular orbital energy levels.
Keywords
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
Tsung-Wen Yen, S.K. Lai,