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関連する概念動画

Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

2.1K
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
2.1K
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

Atomic Nuclei: Nuclear Spin State Population Distribution

2.4K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
2.4K
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

1.3K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis.
1.3K
Nuclear Overhauser Enhancement (NOE)01:06

Nuclear Overhauser Enhancement (NOE)

1.5K
Irradiation of a spin-active nucleus causes an increase or decrease in the signal intensity of neighboring nuclei that are not necessarily chemically bonded or involved in J-coupling. This phenomenon, called the nuclear Overhauser enhancement (NOE), results from through-space interactions between the nuclear spins. The NOE effect decreases with increasing internuclear distance and is generally not observed beyond 4 angstroms. In NOE, dipole-dipole interactions between neighboring spin-active...
1.5K
¹H NMR: Interpreting Distorted and Overlapping Signals01:02

¹H NMR: Interpreting Distorted and Overlapping Signals

1.6K
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are...
1.6K
Second Uniqueness Theorem01:16

Second Uniqueness Theorem

2.7K
Consider a region consisting of several individual conductors with a definite charge density in the region between these conductors. The second uniqueness theorem states that if the total charge on each conductor and the charge density in the in-between region are known, then the electric field can be uniquely determined.
In contrast, consider that the electric field is non-unique and apply Gauss's law in divergence form in the region between the conductors and the integral form to the surface...
2.7K

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関連する実験動画

Updated: Feb 20, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Published on: June 7, 2018

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凍結密度エンベディングのための分析的核二次誘導体は,自己一貫したフィールド方法を使用しています.

Maximilian L Kronenberger1, Sebastian Höfener1

  • 1Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), P.O. Box 6980, 76049 Karlsruhe, Germany.

The Journal of chemical physics
|February 18, 2026
PubMed
まとめ

本研究は,量子化学におけるカップリングされていない凍結密度埋め込み (FDEu) の分析的核二次導出物について紹介しています. この方法は,大きな分子システムの振動周波数を正確に計算し,電荷輸送の研究を支援します.

科学分野:

  • 量子化学とは,量子化学である.
  • コンピューティング・ケミストリー
  • マテリアルサイエンス 材料科学

背景:

  • 分子振動の正確な計算は,化学反応と材料の性質を理解するために不可欠です.
  • Frozen-Density Embedding (FDE) は,より大きな環境にサブシステムを埋め込むことで,大規模なシステムを研究するための計算効率の良い方法を提供します.
  • 解析グラデーションとヘッシアンは,幾何学最適化と振動分析に不可欠です.

研究 の 目的:

  • 結合されていない冷凍密度埋め込み (FDEu) のための分析的な核基底状態第2派生式を導出し,実装する.
  • 弱い結合と強い結合の両方のサブシステムについて,開発された方法の正確性を評価する.
  • 振動周波数計算のための拡張分子システムに対するFDEuアプローチの適用性を実証する.

主な方法:

  • ハートリー・フォックとコーン・シャム密度関数理論におけるFDEuの分析核二次導関数の導出と実装.
  • 精密な核二次導関数と近似核二次導関数を用いた鎖球交換アプローチを用いた交換積分の評価.
  • 超分子計算と比較したFDEu Hessian精度の評価.

主要な成果:

  • FDEu.のための分析核二次導関数の成功派生と実装.

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Experimental and Data Analysis Workflow for Soft Matter Nanoindentation
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Direct Force Measurements of Subcellular Mechanics in Confinement using Optical Tweezers
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Direct Force Measurements of Subcellular Mechanics in Confinement using Optical Tweezers

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関連する実験動画

Last Updated: Feb 20, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Published on: June 7, 2018

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Experimental and Data Analysis Workflow for Soft Matter Nanoindentation
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Experimental and Data Analysis Workflow for Soft Matter Nanoindentation

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  • FDEu Hessianの精度が実証され,様々なコップされたサブシステムに対応しています.
  • 結晶環境に埋め込まれた大型ナフタレンジマー系 (792原子) の振動周波数を計算した.

    • 結論:

    • 開発されたFDEuメソッドは,大型分子システムにおける振動周波数を計算するための正確で効率的なアプローチを提供します.
    • この方法は,電荷輸送現象に関連する分子間振動を分析するための大きな可能性を秘めています.
    • この研究は,さまざまな化学環境におけるFDEuの強みと限界を検証しています.