• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >First principles exploration of crystal structures and physical properties of silicon hydrides KSiH3 and K2SiH6, alkali and alkaline earth metal carbides, and II-V semiconductors ZnSb and ZnAs.
【24h】

First principles exploration of crystal structures and physical properties of silicon hydrides KSiH3 and K2SiH6, alkali and alkaline earth metal carbides, and II-V semiconductors ZnSb and ZnAs.

机译：首先，探讨氢化硅KSiH3和K2SiH6，碱金属和碱土金属碳化物以及II-V半导体ZnSb和ZnAs的晶体结构和物理性质的原理。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

This dissertation is focused on material property exploration and analysis using computational quantum mechanics methods. Theoretical calculations were performed on the recently discovered hexahydride materials A2SiH 6 (A=Rb, K) to calculate the lattice dynamics of the systems in order to check for structural stability, verify the experimental Raman and infrared spectroscopy results, and obtain the theoretical free energies of formation. The electronic structure of the systems was calculated and the bonding and ionic properties of the systems were analyzed. The novel hexahydrides were compared to the important hydrogen storage material KSiH3. This showed that the hypervalent nature of the SiH2-6 ions reduced the Si-H bonding strength considerably. These hydrogen rich compounds could have promising energy applications as they link to alternative hydrogen fuel technology.;The carbide systems Li-C (A=Li, Ca, Mg) were studied using ab initio and evolutionary algorithms at high pressures. At ambient pressure Li2C2 and CaC2 are known to contain C2-2 dumbbell anions and CaC2 is polymorphic. At elevated pressure both CaC2 and Li2C2 display polymorphism. At ambient pressure the Mg-C system contains several experimentally known phases, however, all known phases are shown to be metastable with respect to the pure elements Mg and C. First principle investigation of the configurational space of these compounds via evolutionary algorithms results in a variety of metastable and unique structures.;The binary compounds ZnSb and ZnAs are II-V electron-poor semiconductors with interesting thermoelectric properties. They contain rhomboid rings composed of Zn2Sb2 (Zn2As2) with multi-centered covalent bonds which are in turn covalently bonded to other rings via two-centered, two-electron bonds. Ionicity was explored via Bader charge analysis and it appears that the low ionicity that these materials display is a necessary condition of their multicentered bonding. Both compounds were found to have narrow, indirect band gaps with multi-valley valence and conduction bands; which are important characteristics for high thermopower in thermoelectric materials. Future work is needed to analyze the lattice properties of the II-V CdSb-type systems, especially in order to find the origin of the extremely low thermal conductivity that these systems display.
机译：本文致力于利用计算量子力学方法对材料的性质进行探索和分析。对最近发现的六氢化物材料A2SiH 6（A = Rb，K）进行了理论计算，以计算系统的晶格动力学，以检查结构稳定性，验证实验拉曼光谱和红外光谱结果并获得理论自由能的形成。计算了系统的电子结构，并分析了系统的键合和离子性质。将新型六氢化物与重要的储氢材料KSiH3进行了比较。这表明SiH2-6离子的高价性质大大降低了Si-H键合强度。这些富氢化合物可能与替代氢燃料技术联系起来，具有广阔的能源应用前景。在高压下，采用从头算和演化算法研究了碳化物体系Li-C（A = Li，Ca，Mg）。在环境压力下，已知Li2C2和CaC2包含C2-2哑铃状阴离子，而CaC2是多晶型的。在高压下，CaC2和Li2C2均显示出多态性。在环境压力下，Mg-C系统包含几个实验已知的相，但是，相对于纯元素Mg和C，所有已知的相均显示为亚稳态。通过进化算法对这些化合物的构型空间进行的第一原理研究得出：二元化合物ZnSb和ZnAs是具有有趣热电特性的II-V电子贫乏半导体。它们包含由具有多中心共价键的Zn2Sb2（Zn2As2）组成的菱形环，这些共价键又通过两个中心的两个电子键与其他环共价键合。通过Bader电荷分析探索了离子性，看来这些材料显示出的低离子性是它们多中心键合的必要条件。发现这两种化合物具有窄的，间接的带隙，具有多谷价和导带。这是热电材料中高热功率的重要特征。需要进一步的工作来分析II-V CdSb型系统的晶格特性，尤其是为了找到这些系统所显示的极低导热率的起源。

著录项

  • 作者

    Benson, Daryn Eugene.;

  • 作者单位

    Arizona State University.;

  • 授予单位 Arizona State University.;
  • 学科 Chemistry Physical.;Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 165 p.
  • 总页数 165
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号