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.

本项目的目的是用X射线散射技术研究和理解面内插层Ba2+形成的纳米结构硅笼高压诱导相变的机理。在NIV，V阈值以上，嵌入态的钡原子呈现出所谓的“巨偶极共振”。嵌入原子的电子结构和局域环境的变化强烈地影响着这种共振的整体形状和起始位置。因此，共振是根据压力引起的相变进行同样变化的非常敏感的探头。这种变化将首先研究不同类型的Ba/Si化合物，其中嵌入了不同的硅环境，包括硅纳米笼子和沟道结构。包合物Ba8Si46和Ba24Si100的高压性质也将在高达25 Gpa的压力范围内进行研究，以详细了解相应相变的机制。在文献中，它们在偏心位置、硅空位形成和电子重新配置方面有争议地讨论。这些实验将使用非共振非弹性x射线散射(NRIXS)来完成，这使得能够用硬x射线测量低能量激发。这是研究极端压力条件下钡巨人共振的独特方法，在极端压力条件下，不使用软X射线和电子作为探针。所有的实验研究都将伴随着用实空间多重散射方法在随时间变化的局域密度近似下计算测量光谱。这种利用NRIXS对巨共振的高压研究具有很大的潜力，可以作为一种独特的探针，同时研究一大类纳米结构材料的局域结构和一般电子性质。

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