Na原子链表面等离激元特性的含时密度泛函研究

The study of the surface plasmon characters of Na atomic chains based on time-dependent density functional theory

本文用含时密度泛函理论研究了线性Na原子链的表面等离激元机理.主要在原子尺度下模拟计算了体系随着原子数增加及原子间距变化的集体激发过程.研究发现线性原子链有一个普遍的特性——存在一个纵模和两个横模.两个横模一般在实验上很难被观测到.纵模随着原子链长度增加,能量红移的同时,该纵模主峰的强度呈线性增长.随着原子个数的增加,端点模式(TE)开始蓝移,能量和偶极强度都逐渐趋向饱和.横模能量被劈裂的原因概括如下:(一)每个位置的电子受到的势不同,在两端的电子受到的势要比在中间的电子受到的势要高,因此两端的电荷积累也比中间多;(二)端点存在悬挂键,所以中间的电子-电子间相互作用与端点的不一样,这两方面又都与原子间距d有关.

This paper explored the mechanism of the coupling of Plasmon excitation of linear Na atomic chains using the time-dependent density function theory.We simulated the process of the collective electronic excitation as chains and interatomic distance d increase.There is a common characteristic-a longitudinal(L)mode and two transverse modes(T)which is generally difficult to be observed.The energy of the L mode shows redshift and intensity of the L mode increases linearly with the increase of atom number.The energy splitting in transvers Plasmon resonance can be explained by the two factors:one is the electron potential,which is dependent on the position of the atoms along the chain which is the highest at the two ends and lower in the middle of the chain;the other is electron-electron interaction,which is different between the end and the central atoms due to the dangling bond at the end.Both quantities are dependent on the interatomic spacing d.