The lowest energy structure and magnetic properties of metallic and covalent clusters

• Main Authors: Tsung-Wen Yen, 顏聰文
• Other Authors: San-Kiong Lai
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/24100060280409791262

博士 === 國立中央大學 === 物理學系 === 104 === In the first part, we proposed a modified basin hopping method which is very robust in searching the lowest energy structure of carbon clusters CN ( N=3-24). Due to the intricate coupling among ions and valence electrons in covalent systems, an unbiased optimization is necessary to locate the lowest energy structures. We have obtained the topological transition from a linear chain, a monocyclic ring to a polycyclic ring, and a fullerene/cage-like geometry and we also compared our structural findings with theoretical works in this field. In the second part of the thesis we first utilized a state-of-the-art algorithm that applies the empirical Gupta potential to search for the lowest energy structures of AgnCu38-n bimetallic clusters. We investigated from the results of DFT the charge density and spin charge density dispersions as well as magnetic properties of this system. It was found that the clusters at n=1-4, 24 as well as the two pure clusters Ag and Cu uncommonly carry net magnetic moments. We invoked the point group theory to explain these unexpected magnetism by analyzing the molecular orbital energy levels (MOELs) of these clusters. The MOELs were, however calculated by symmetry restricted DFT. and proposed to use point group theory for further explanation of these unexpected net magnetism.