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相关概念视频

Molecular and Ionic Solids02:54

Molecular and Ionic Solids

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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...
16.9K
Network Covalent Solids02:18

Network Covalent Solids

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Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
13.4K
Van der Waals Equation01:10

Van der Waals Equation

4.0K
The ideal gas law is an approximation that works well at high temperatures and low pressures. The van der Waals equation of state (named after the Dutch physicist Johannes van der Waals, 1837−1923) improves it by considering two factors.
First, the attractive forces between molecules, which are stronger at higher densities and reduce the pressure, are considered by adding to the pressure a term equal to the square of the molar density multiplied by a positive coefficient a. Second, the volume...
4.0K
Crystal Field Theory - Tetrahedral and Square Planar Complexes02:46

Crystal Field Theory - Tetrahedral and Square Planar Complexes

41.5K
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,...
41.5K
Structures of Solids02:22

Structures of Solids

14.0K
Solids in which the atoms, ions, or molecules are arranged in a definite repeating pattern are known as crystalline solids. Metals and ionic compounds typically form ordered, crystalline solids. A crystalline solid has a precise melting temperature because each atom or molecule of the same type is held in place with the same forces or energy. Amorphous solids or non-crystalline solids (or, sometimes, glasses) which lack an ordered internal structure and are randomly arranged. Substances that...
14.0K
Molecular Comparison of Gases, Liquids, and Solids02:26

Molecular Comparison of Gases, Liquids, and Solids

40.5K
Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no regular arrangement (no fixed shape); in a gas, they are far apart with no regular arrangement (no fixed shape). Particles in a solid vibrate about fixed positions (cannot flow) and do not generally move in relation to one another; in a liquid, they move past each other (can flow) but remain in essentially constant contact; in a gas, they move...
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相关实验视频

Updated: Jun 6, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
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评估固体精确密度的交换相关函数.

Ayoub Aouina1,2,3, Pedro Borlido4, Miguel A L Marques1,3

  • 1Research Center Future Energy Materials and Systems of the University Alliance Ruhr and Interdisciplinary Centre for Advanced Materials Simulation, Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany.

Journal of chemical theory and computation
|December 3, 2024
PubMed
概括
此摘要是机器生成的。

科恩-沙姆密度函数理论 (KS-DFT) 依赖于其交换相关函数的近似. 这项研究使用固态数据评估这些函数,发现那些遵守确切约束的函数在能量和密度预测方面表现最好.

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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
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Thermochemical Studies of NiII and ZnII Ternary Complexes Using Ion Mobility-Mass Spectrometry
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相关实验视频

Last Updated: Jun 6, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
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Thermochemical Studies of NiII and ZnII Ternary Complexes Using Ion Mobility-Mass Spectrometry
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科学领域:

  • 凝聚物质物理学 凝聚物质物理学
  • 量子化学 是一个量子化学.
  • 计算材料科学科学 计算材料科学

背景情况:

  • 科恩-沙姆密度函数理论 (KS-DFT) 对于从第一原理预测电子属性至关重要.
  • KS-DFT的准确性取决于近似交换相关函数,该函数由确切的约束指导.
  • 目前的近似方法是否优先考虑精确的能量精度而不是精确的密度表示存在争论.

研究的目的:

  • 为了研究各种交换相关函数在雅各布梯的不同阶段的性能.
  • 评估固体材料的能量和密度预测的功能性能.
  • 评估在功能设计中纳入确切约束的影响.

主要方法:

  • 对于三个代表性固体: (半导体),化 (绝缘体) 和铜 (金属) 的密度和能量几乎完全相同.
  • 对比了多个交换相关函数的性能,跨越半局部,混合和元混合类别.
  • 分析了每个函数的能量和密度预测中的错误.

主要成果:

  • 一些混合和半局部函数在预测能量和密度方面表现一致.
  • 设计以满足精确约束的功能通常在所有材料类型中排名在最佳表现者中.
  • 在2000年代初之前开发的函数式数据显示,与一些较新的数据相比,同时改善能量和密度预测的趋势更好.

结论:

  • 该研究支持使用精确约束来构建更可靠的交换相关函数.
  • 在能量和密度预测中存在错误的相关演变,即使在最近的功能发展中也是如此.
  • 这些发现为选择和开发固态材料准确的KS-DFT函数提供了宝贵的见解.