螺旋状ヒップリック酸結晶の成長中の可逆の回転
Alexander G Shtukenberg1, John Freudenthal, Bart Kahr
1Crystallography Department, St. Petersburg State University, Universitetskaya emb., 7/9, 199034, St. Petersburg, Russia. shtukenberg@mail.ru
Journal of the American Chemical Society
|April 22, 2010
まとめ
ヒップリック酸のマクロスコーピック結晶は,成長過程で可逆的な歪みと解き方をし,この現象はダイナミックな弾性ストレスによって引き起こされ,最終的には結晶の形状を形作ります.
科学分野:
- クリスタログラフィーです.
- 材料科学 材料科学とは
- 固体物理 固体物理学
背景:
- 結晶の成長は,固定された方向を想定して,通常,単位を順番に追加することを意味します.
- これまでの結晶形態学のモデルは,成長中のダイナミックで可逆的な形状の変化を完全に説明できませんでした.
研究 の 目的:
- 成長中のマクロスコープのヒップリック酸結晶の可逆的な歪みと解き方を調査し,実証する.
- 観測された結晶光学特性と動的成長プロセスとの関係を確立する.
主な方法:
- 低冷却の溶融物におけるヒップリック酸結晶の成長の現地観察.
- ミュラー行列顕微鏡を用いた結晶光学特性の測定.
- 弾性ストレスとその形態学的変化における役割の分析.
主要な成果:
- ヒプリカ酸の結晶は,成長の過程で,伸びの軸の周りに可逆的な歪みと解き方を表します.
- 弾性ストレスによって引き起こされる回転と解離のダイナミックな相互作用が,結晶の最終形状を決定する.
- 測定された光学特性は,成長フロントの光学指標の螺旋回転と相関する.
結論:
- リバーシブルな回転と解離は,マクロスコープの結晶形態学における重要な要因であり,従来の成長モデルに挑戦しています.
- この発見は,螺旋状の構造を示す様々な分子および鉱物結晶に適用できる新しい力学的理解を提供します.
- 螺旋結晶の成長に対する既存の力法則関係における歪みを解き放つことの意味を探るため,さらなる研究が必要である.
関連する概念動画
Radical Chain-Growth Polymerization: Chain Branching
The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
Radical Chain-Growth Polymerization: Mechanism
The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this species into the...
Crystal Growth: Principles of Crystallization
Crystallization is a phase transformation process in which crystals are precipitated from a supersaturated solution or formed from other sources. During crystallization, atoms or molecules arrange themselves into a well-defined, rigid crystal lattice to minimize energy.
Initiating crystallization involves manipulating the concentration of the solute and the temperature of the solution. Since crystal growth occurs when the ratio of concentration and solubility of the solute in the solvent – the...
Initiating crystallization involves manipulating the concentration of the solute and the temperature of the solution. Since crystal growth occurs when the ratio of concentration and solubility of the solute in the solvent – the...
Woodward–Hoffmann Selection Rules and Microscopic Reversibility
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
Ziegler–Natta Chain-Growth Polymerization: Overview
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...
Chair Conformation of Cyclohexane
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...


