A novel approach to study pressure-induced phase transitions of nano-structured materials: The barium giant dipole resonance

研究纳米结构材料压力诱导相变的新方法：钡巨偶极子共振

• 批准号: 88286259
• 负责人: Professor Dr. Metin Tolan
• 金额: --
• 依托单位: Lehrstuhl für Experimentelle Physik I
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2008
• 资助国家: 德国
• 起止时间: 2007-12-31 至 2013-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/88286259?language=en
• 关键词: novel; approach; study; pressure; induced

The aim of this project is to study and understand the mechanism of high pressure induced phase transitions for nano-structured silicon clathrates with endohedrally intercalated barium atoms by x-ray scattering techniques. The intercalated barium atoms show a so-called “giant dipole resonance” above the NIV,V -threshold. The overall shape and onset of this resonance is strongly affected by changes of both the electronic structure and the local environment of the embedded atom. Thus, the resonance is a very sensitive probe for likewise changes according to pressure induced phase transitions. Such changes will be investigated first for different types of Ba/Si compounds in which barium is embedded into various silicon surroundings including silicon nano-cages and channel structures. The high pressure properties of the clathrates Ba8Si46 and Ba24Si100 will also be studied within a pressure range up to 25 GPa in order to understand in detail the mechanism of the corresponding phase transitions. They are controversially discussed in the literature in terms of off-center positions, silicon vacancy formation and electronic reconfiguration. The experiments will be accomplished using non-resonant inelastic x-ray scattering (NRIXS) which enables the measurement of low energy excitations with hard x-rays. This is a unique way to study barium giant resonances under extreme pressure conditions where the use of soft x-rays and electrons as probes is excluded. All experimental investigations will be accompanied by computations of measured spectra by means of a realspace multiple scattering approach within the time dependent local density approximation. Such high pressure studies of giant resonances using NRIXS have great potential to serve as a unique probe for the simultaneous study of local structures and electronic properties in general for a wide class of nano-structured materials.

该项目的目的是通过X射线散射技术研究和理解纳米结构硅外层的高压诱导相变的机理。插入的钡原子在NIV v-阈值上方表现出所谓的“巨型偶极子共振”。这种共振的整体形状和发作受到嵌入原子的电子结构和局部环境的变化的强烈影响。这，共振是一种非常敏感的探测器，同样根据压力诱导的相变而变化。将首先研究此类变化，用于不同类型的BA/SI化合物，其中钡嵌入包括硅纳米型和通道结构在内的各种硅周围环境中。围墙BA8SI46和BA24SI100的高压性能也将在最高25 GPA的压力范围内进行研究，以详细了解相应的相变的机理。在文献中始终讨论它们，从中心位置，硅空置形成和电子重新配置。实验将使用非共振非弹性X射线散射（NRIX）来完成，该散射（NRIX）可以用硬X射线测量低能兴奋。这是在极端压力条件下研究钡巨型共振的独特方法，在极端压力条件下，将软X射线和电子产品作为问题排除在外。所有实验研究将通过在时间依赖的局部密度近似值内通过Realspace多散射方法来计算测量光谱的计算来完成所有实验研究。使用NRIX对巨大共振的高压研究具有巨大的潜力，可以作为对局部结构和电子特性的最简单研究的独特探针，总体上针对宽类纳米结构材料。

项目成果

Structural changes in amorphous GexSiOy on the way to nanocrystal formation

• DOI: 10.1088/0957-4484/24/16/165701
• 发表时间: 2013-04
• 期刊: Nanotechnology
• 影响因子: 3.5
• 作者: A. Nyrow;C. Sternemann;C. Sahle;A. Hohl;M. Zschintzsch-Dias;A. Schwamberger;K. Mende;I. Brinkmann;M. M. Sala-M.;R. Wagner;A. Meier;F. Völklein;M. Tolan

The Ba 4d–4f giant dipole resonance in complex Ba/Si compounds

复杂 Ba/Si 化合物中的 Ba 4dâ4f 巨偶极共振

• DOI: 10.1088/0953-4075/47/4/045102
• 发表时间: 2014
• 期刊: Journal of Physics B: Atomic, Molecular and Optical Physics
• 作者: Ch.J. Sahle;C. Sternemann;H. Sternemann;J.S. Tse;R.A. Gordon;S. Desgreniers;S. Maekawa;S. Yamanaka;F. Lehmkühler;D.C.F. Wieland;K. Mende;S. Huotari;M. Tolan
• 通讯作者: M. Tolan