ペンタ・ツイン・バイピラミッドまたはマイクロクリスタルにおける環境安定のテトラゴナルおよびオルソロンビック相
Gangaiah Mettela1, Meha Bhogra, Umesh V Waghmare
1Thematic Unit of Excellence on Nanochemistry and Chemistry and Physics of Materials Unit and ‡Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) , Jakkur P.O., Bangalore 560 064, India.
Journal of the American Chemical Society
|February 12, 2015
まとめ
研究者らは,金 (Au) マイクロクリスタルで,体中心の四角形 (bct) と体中心のオーソロンビック (bco) 段階の新しい結晶構造を発見した. これらの非面中心の立方体 (fcc) 段階は,二ピラミッド形の金構造の幾何学的なストレートから生じる.
科学分野:
- 材料科学 材料科学とは
- 固体物理 固体物理学
- ナノテクノロジー ナノテクノロジー
背景:
- 大量ゴールドは,通常,面中心の立方体 (fcc) の結晶構造を示します.
- 金の構造的多様性を理解することは,高度なアプリケーションにとって極めて重要です.
- これまでの研究は主に黄金のfcc相に焦点を当てていました.
研究 の 目的:
- 二ピラミッド形の金マイクロ結晶の結晶構造を調査するために.
- 現存する非fcc相を特定し,特徴づけます.
- これらの新しい金相の形成機構と安定性を理解するために.
主な方法:
- テトラオクティラモニウムブロミド (ToABr) で安定した (AuCl4) (((-) の熱分解によるバイピラミダルAuマイクロ結晶の合成.
- 結晶構造を検出するために,実験室の単色X線源を用いた特徴付け.
- 第一原則 段階安定性に関する実験的発見を裏付けるための理論的計算.
主要な成果:
- Au微結晶における体中心の四角形 (bct) と体中心の正方形 (bco) 段階の発見.
- これらの非fcc相は,ペンタ双子の先を持つ二ピラミッド形金で観察されました.
- 非fcc相の形成は,200~250°Cの温度範囲内の幾何学的に誘発されたストレインと関連しています.
結論:
- 二ピラミッド形の金マイクロクリスタルにおける幾何学的に誘導されたストレンは,非fcc相 (bctとbco) を安定させることができる.
- 柔らかいモードは,これらの非fcc Au構造のストレス下での温度依存の安定性の起源として特定されています.
- 高温アニリングはストレスを軽減し,非fcc相の不安定化につながり,ゴールドを典型的なfcc構造に戻します.
関連する概念動画
01:29Crystallographic Point Groups
108
Crystallographic point groups represent the various symmetry operations that can occur within crystals. They are unique in that at least one point will always remain unchanged during these actions. For instance, consider the triclinic system. This system, devoid of any axis or plane of symmetry, aligns with the C1 and Ci point groups.where Cᵢ is characterized solely by a center of inversion.Contrastingly, the monoclinic system introduces an element of symmetry. This system with one plane...
108
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
50.1K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than...
50.1K
01:24The Seven Crystal Systems: Overview
245
Crystals with various point group symmetries belong to different crystal classes, which are synonymous terms. Despite being in the same class, crystals may have distinct shapes, like cubes and octahedra. There are 32 three-dimensional point groups, all of which are systematically divided into seven crystal systems.The basic cubic crystal system, exemplified by NaCl, features orthogonal vectors (α = β = �� = 90°) of equal lengths (a = b = c). When specific...
245
02:42Ionic Crystal Structures
21.7K
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
21.7K
02:37Metallic Solids
21.6K
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and...
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and...
21.6K
02:22Structures of Solids
22.5K
Solids in which the atoms, ions, or molecules are arranged in a definite repeating pattern are known as crystalline solids. Metals and ionic compounds typically form ordered, crystalline solids. A crystalline solid has a precise melting temperature because each atom or molecule of the same type is held in place with the same forces or energy. Amorphous solids or non-crystalline solids (or, sometimes, glasses) which lack an ordered internal structure and are randomly arranged. Substances that...
22.5K