液体の水中の六角氷 (Ih) の核化
Ravi Radhakrishnan1, Bernhardt L Trout
1Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Journal of the American Chemical Society
|June 19, 2003
まとめ
研究者らは,水が氷に凍りつく (Ih) の難解な核形成過程を観察した. 先進的なモンテカルロシミュレーションを用いて,液体状態から結晶状固体状態への移行を詳細に説明しました.
科学分野:
- 物理化学 物理化学について
- マテリアルサイエンス 材料科学
- 計算物理学の物理
背景:
- 超冷却した液体から安定した結晶型固体の形成である核化は,実験的・計算的研究が困難である.
- 重要な核の統計的性質と一時的な存在は,既存のデータとシミュレーション結果に重大な不確実性をもたらします.
研究 の 目的:
- 環境条件下での液体の水の凍結過程における核化プロセスの詳細で定量的に正確な観察を提供するため.
- 液体の水と氷 (Ih) の間の中間状態を相変化の過程で特徴づける.
主な方法:
- ノン-ボルツマンサンプリング・モンテカルロ・アプローチを用いた.
- システムの結晶性を統計的に特徴付けるために一連の順序パラメータを使用した.
- 液体の水から氷への移行 (Ih) 中の分析された中間状態.
主要な成果:
- 凍結時のシステムの性質の統計的に平均された記述を達成しました.
- 液体の水と氷 (Ih) の間の中間状態におけるシステムの順序を特徴づけた.
- 水核化の過程の定量的な観察を提供した.
結論:
- この研究では,水が凍って氷 (Ih) になる核形成過程を成功裏に記述しました.
- 採用された方法論は,難解な相変遷を研究するための新しい方法を提供します.
- この研究は,凝縮物質系における結晶化の理解を深める.
関連する概念動画
01:23States of Water
Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the intermolecular forces that draw molecules together and ii) the kinetic energy that leads to movements that pull them apart.
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
03:13Intermolecular Forces
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
02:54Molecular and Ionic Solids
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
02:42Ionic Crystal Structures
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...
03:13Intermolecular Forces
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...