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相关概念视频

Atomic Structure01:33

Atomic Structure

Overview
Nuclear Stability03:18

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together in the...
Electronic Structure of Atoms02:28

Electronic Structure of Atoms


An atom comprises protons and neutrons, which are contained inside the dense, central core called the nucleus, with electrons present around the nucleus. Taking into account the wave–particle duality of electrons and the uncertainty in position around the nucleus, quantum mechanics provides a more accurate model for the atomic structure. It describes atomic orbitals as the regions around the nucleus where electrons of discrete energy exist, characterized by four quantum numbers:  n, l, ml, and...
Atomic Nuclei: Nuclear Spin State Overview01:03

Atomic Nuclei: Nuclear Spin State Overview

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...
Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
Atomic Structure01:17

Atomic Structure

The Greek philosopher Democritus proposed that everything on Earth is made up of tiny particles called atomos, Greek for "indivisible," from which the modern term "atom" is derived. In the 19th century, John Dalton proposed the atomic theory that is still largely correct today. He put forth five postulates to explain how atoms made up the world around us. (1) All matter is composed of infinitely small particles or atoms. (2) All atoms of a given element are identical to one another and (3) are...

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Updated: May 8, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
14:44

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Published on: December 16, 2013

确定纳米级原子结构的问题.

Simon J L Billinge1, Igor Levin

  • 1Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA. billinge@pa.msu.edu

Science (New York, N.Y.)
|April 28, 2007
PubMed
概括
此摘要是机器生成的。

由于当前方法的局限性,确定纳米级材料的原子结构具有挑战性. 为这些复杂的功能材料提出了一种结合理论和实验的新"复杂建模"方法.

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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
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Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

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Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations
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Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations

Published on: October 12, 2019

相关实验视频

Last Updated: May 8, 2026

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
14:44

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Published on: December 16, 2013

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
14:55

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy

Published on: September 17, 2017

Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations
13:56

Probe Type II Band Alignment in One-Dimensional Van Der Waals Heterostructures Using First-Principles Calculations

Published on: October 12, 2019

科学领域:

  • 材料科学 材料科学 材料科学
  • 纳米技术 纳米技术
  • 结构分析 结构分析

背景情况:

  • 新兴的复杂功能材料主要在纳米尺度上表现出原子秩序.
  • 现有的晶体学方法不足以确定这些纳米结构材料的原子结构.
  • 迫切需要新的,广泛适用的,定量和强大的纳米尺度结构确定方法.

研究的目的:

  • 提供各种类型的纳米结构材料的概述.
  • 审查目前研究纳米结构材料结构的方法.
  • 为纳米尺度结构确定提出一个新的范式.

主要方法:

  • 对纳米结构材料及其表征技术的现有文献的审查.
  • 分析目前纳米级结构分析方法的局限性.
  • 概念框架的发展,为一个概念框架的发展.
  • 复杂的建模复杂的建模.
  • 一个范式. 一个范式.

主要成果:

  • 确定纳米级原子结构确定中的关键挑战.
  • 目前的概述,虽然有限,纳米结构分析的技术.
  • 关于综合计算框架的建议,该框架将理论和实验结合起来.

结论:

  • 目前的方法无法充分解决纳米级材料的原子结构.
  • 一种涉及材料科学,物理,化学,计算机科学和应用数学的多学科方法是必不可少的.
  • 一个"复杂建模"范式,将理论和实验集成到一个自相一致的计算框架中,为纳米级结构确定提供了一个有希望的解决方案.