二维声子晶体色散关系的大尺度晶格动力学计算  

Large scale lattice dynamics calculation for phonon dispersion relation of two-dimensional phononic crystals

作　　者：魏志勇[1,2] 蒋永强[1,2] 毕可东[1,2] 杨决宽[1,2] 陈云飞[1,2] Wei Zhiyong;Jiang Yongqiang;Bi Kedong;Yang Juekuan;Chen Yunfei(School of Mechanical Engineering, Southeast University , Nanjing 211189 , China;Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University , Nanjing 211189 , China)

机构地区：[1]东南大学机械工程学院,南京211189 [2]东南大学江苏省微纳生物医疗器械设计与制造重点实验室,南京211189

出　　处：《东南大学学报（自然科学版）》2017年第3期495-499,共5页Journal of Southeast University：Natural Science Edition

摘　　要：提出了一种计算大尺度原胞的晶格动力学方法,对光滑硅薄膜的声子色散关系进行了检验.在不考虑声子区域折叠效应的条件下,通过比较超原胞和单原胞模型计算的声子色散关系,证实了所提方法的正确性.运用该方法研究了二维孔状硅声子晶体的色散关系.进一步研究了硅声子晶体色散关系与气孔率和膜厚的关系,结果发现,与相同厚度的光滑硅薄膜相比,孔的存在降低了三支声学的声子群速度;随着气孔率的增加,声子群速度快速降低;而增加薄膜厚度主要增加了法向声子群速度.A lattice dynamics technique for phonon dispersion of large scale unit cell was developed in this paper,and is used to check the phonon dispersion of the smooth silicon film.The comparison of the phonon dispersion between the super unit cell model and the single unit cell model confirmed the validity of the technique without considering the zone folding effects.The technique was performed to investigate the phonon dispersion relation of two-dimensional porous silicon phononic crystals.Compared with smooth silicon film with same thickness,it was found that the introduction of the pore reduced the phonon group velocity of three acoustic phonon branches.The effects of the porosity and the thickness of the silicon phononic crystals on the phonon dispersion relation were further investigated.The results shown that the phonon group velocity for all modes decreases sharply with increasing porosity;while increasing the thickness mainly increases the group velocity of ZA(flexible acoustic)modes.The present investigation provides an important guide for modulating the thermal conductivity of phononic crystals.

关 键 词：声子晶体 晶格动力学 色散关系 群速度 

分 类 号：O484.4[理学—固体物理]