NaCN的压致结构相变和电子特性研究
时间:2020-06-21 15:08 来源:毕业论文 作者:毕业论文 点击:次
| 摘要 本文研究了 NaCN 在高压下的结构相变，并对其结构和弹性特征及电子特性进行研究。本文运用基于遗传算法的结构程序对 NaCN的结构相变序列进行计算，研究了实验确定的Pmmn、Cm结构和预测得到的 P-1、Immm-2结构，并发现在10 GPa下Cm转变为 R3m，在16 GPa下P-1 变为 Immm-2，在30 GPa下 Pmmn转变为R3m。通过对在给定压力下 NaCN这些结构的研究得到：P-1结构中有C3N2和CN2，Immm-2 结构中有碳氮六元环。弹性模量的计算结果，说明了这四个结构是力学稳定的。通过能带和 DOS 图分析得到四个结构的NaCN都是间接带隙半导体。但在压力为 23 GPa时，Immm-2 结构的 NaCN是金属。 该论文有图3幅，表 2个，参考文献 20篇。 51406 毕业论文关键词：高压 结构相变 弹性模量 电子特性 Pressure-induced Structural Phase Transformation and Electronic-properties of NaCN Abstract In this paper, the structurale phase transition of NaCN under high pressure is studied based on genetic algorithm, and elastic characteristics and electronic properties of discussed phases are studied using first-principles total energy calculation. The structure phase transformation sequence of NaCN was obtained.Besides P-1 and Immm-2 predicted,both Pmmn and Cm determined by experiment were included in our study. Cm transformed into R3m at 10 GPa, Phase P-1 transformed into Immn-2 at 16 GPa,Phase Pmmn transformed into R3m at 30 GPa. P-1 structure include C3N2 and CN2, Carbon atoms and nitrogen atoms in Immm-2 structure are polymerized to form six-membered ring. The calculat elastic moduli show that the four structures are mechanically stable. The obtained band structures conclude that four phases are indirect band gap semiconductors. When the pressure is 23 GPa, Immm-2 phase is metal. Key Words : high pressure phase transition elastic modulus electronic property 目录 摘要.I AbstractII 目录.Ⅲ 图清单.IV 表清单.IV 1绪论.1 1.1氰化钠的研究背景1 1.2氰化钠的研究目的和意义1 1.3本文的主要内容2 2理论基础.3 2.1密度泛函理论3 2.2第一性原理4 2.3固体结构与高压相变4 2.4能带理论5 2.5弹性特征6 2.6计算运用的软件6 3NaCN的结构相变、力学及电子特性7 3.1NaCN压致结构相变研究7 3.2弹性特征.10 3.3电子特性研究.12 4总结与展望.15 参考文献.16
致谢.18 |