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相关概念视频

Crystal Field Theory - Tetrahedral and Square Planar Complexes02:46

Crystal Field Theory - Tetrahedral and Square Planar Complexes

41.8K
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 the dxy,...
41.8K
Crystal Field Theory - Octahedral Complexes02:58

Crystal Field Theory - Octahedral Complexes

26.3K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
26.3K
X-ray Diffraction of Biological Samples01:10

X-ray Diffraction of Biological Samples

3.8K
X-ray diffraction or XRD is an analytical tool that utilizes X-rays to study ordered structures such as crystalline organic and inorganic samples, polycrystalline materials, proteins, carbohydrates, and drugs.
According to Bragg's law, when X-rays strike the sample positioned on a stage, the rays are  scattered by the electron clouds around the sample atoms. The  X-ray diffraction or scattering is caused by constructive interference of the X-ray waves that reflect off the internal...
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Predicting Molecular Geometry02:27

Predicting Molecular Geometry

34.2K
VSEPR Theory for Determination of Electron Pair Geometries
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X-ray Crystallography02:18

X-ray Crystallography

23.8K
The size of the unit cell and the arrangement of atoms in a crystal may be determined from measurements of the diffraction of X-rays by the crystal, termed X-ray crystallography.
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...
23.8K
Valence Bond Theory02:42

Valence Bond Theory

8.5K
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
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相关实验视频

Updated: Jun 17, 2025

Achieving Efficient Fragment Screening at XChem Facility at Diamond Light Source
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Achieving Efficient Fragment Screening at XChem Facility at Diamond Light Source

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dxtb-一个高效和完全可区分的框架,用于扩展紧固结合.

Marvin Friede1, Christian Hölzer1, Sebastian Ehlert2

  • 1Mulliken Center for Theoretical Chemistry, University of Bonn, Bonn 53115, Germany.

The Journal of chemical physics
|August 9, 2024
PubMed
概括

我们介绍了dxtb,这是一个Python框架,用于可微分的半实证扩展紧固结合 (xTB) 方法. 它可以有效计算分子性质,并将量子化学与机器学习相结合.

科学领域:

  • 计算化学的计算化学
  • 机器学习 机器学习
  • 量子化学 是一个量子化学.

背景情况:

  • 自动区分 (AD) 对于机器学习优化至关重要.
  • 现在,AD的实用性已经在量子化学中被认可,用于导数计算.
  • 半经验扩展紧密结合 (xTB) 方法提供了准确性和计算成本的平衡.

研究的目的:

  • 介绍dxtb,一个开源的,完全可区分的xTB方法框架.
  • 为了实现分子性质的高效计算,并促进机器学习的整合.
  • 为以物理为灵感的端到端可微分模型提供基础.

主要方法:

  • 在Python中开发,使用PyTorch进行数组运算.
  • 实现了全面的代码向量化和优化,以提高计算效率.
  • 杆自动区分用于计算任意顺序的衍生品.

主要成果:

  • dxtb的性能与小分子编译的xTB程序相美.
  • 能源评估与现有计划是一致的.
  • 自动差异化核衍生品比分析类衍生品慢2-5倍.
  • 在计算分子和光谱性质方面证明了实用性.

更多相关视频

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相关实验视频

Last Updated: Jun 17, 2025

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Online Size-exclusion and Ion-exchange Chromatography on a SAXS Beamline
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Online Size-exclusion and Ion-exchange Chromatography on a SAXS Beamline

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结论:

  • dxtb简化了量子化学中的优化和属性评估.
  • 它促进了半经验量子化学与机器学习的无整合.
  • 该框架推进了半经验方法,并支持混合机器学习应用程序.