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相关概念视频

Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

3.1K
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
3.1K
Crystal Field Theory - Tetrahedral and Square Planar Complexes02:46

Crystal Field Theory - Tetrahedral and Square Planar Complexes

40.7K
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...
40.7K
Polymers: Defining Molecular Weight01:01

Polymers: Defining Molecular Weight

2.7K
Unlike small molecules with definite molecular weights, polymers are a mixture of individual polymer chains of varying lengths, each with a unique molecular weight.  So, the molecular weight of a polymer is expressed as an average value based on the average size of the polymer chains. The two most common forms of averages used for polymers are the number average molecular weight and weight average molecular weight.
The number average molecular weight (Mn) is the summation of the number...
2.7K
Crystal Field Theory - Octahedral Complexes02:58

Crystal Field Theory - Octahedral Complexes

25.7K
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...
25.7K
Molecular Models02:00

Molecular Models

37.5K
Physical models representing molecular architectures of chemical compounds play essential roles in understanding chemistry. The use of molecular models makes it easier to visualize the structures and shapes of atoms and molecules.
37.5K
Molecular Weight of Step-Growth Polymers01:08

Molecular Weight of Step-Growth Polymers

2.1K
Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
2.1K

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相关实验视频

Updated: May 12, 2025

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics
10:52

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics

Published on: April 12, 2019

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聚合物自相一致场和密度函数理论的统一计算框架.

Jiawei Zhang1, Baohui Li1, Qiang Wang2

  • 1School of Physics, Nankai University, No. 94 Weijin Rd., Tianjin 90001, P. R. China.

Journal of chemical theory and computation
|May 9, 2025
PubMed
概括

我们将聚合物密度功能理论 (PDFT) 统一到一个单一的计算框架中,提高了聚合物模拟的数值精度. 这一进步使得PDFT计算与复杂聚合物系统的自相一致场理论 (SCFT) 相比.

科学领域:

  • 计算物理和化学 计算物理和化学
  • 聚合物科学与工程 聚合物科学与工程

背景情况:

  • 聚合物密度功能理论 (PDFT) 为模拟聚合物系统提供了一种强大的方法.
  • 现有的PDFT方法可能是计算密集型和复杂的实现.
  • 自相一致的场理论 (SCFT) 是一种成熟的聚合物模拟方法.

研究的目的:

  • 为各种PDFTs开发一个统一的计算框架.
  • 显著提高PDFT计算的数值精度.
  • 为了比较新的PDFT框架与SCFT的效率和准确性.

主要方法:

  • 将各种PDFT重新构成一个统一的计算框架.
  • 实现对真实空间和相互空间计算的数值增强.
  • 该框架应用于有限的触角硬球和软球聚合物链.

主要成果:

  • 成功将各种PDFT统一到一个单一的,连贯的计算框架中.
  • 在PDFT计算中的数值精度显著提高.
  • 初步结果显示,该框架能够实现高精度的3D PDFT模拟.
  • 对于长聚合物链,PDFT计算的计算复杂性与SCFT计算复杂性相当.

更多相关视频

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package
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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package

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相关实验视频

Last Updated: May 12, 2025

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics
10:52

Multiscale Sampling of a Heterogeneous Water/Metal Catalyst Interface using Density Functional Theory and Force-Field Molecular Dynamics

Published on: April 12, 2019

12.7K
Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
12:11

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

Published on: April 8, 2020

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Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package
06:37

Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package

Published on: September 17, 2021

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结论:

  • 统一的PDFT框架为聚合物模拟提供了更容易访问和更准确的工具.
  • 这种方法弥合了PDFT和SCFT之间的差距,提供了一种多功能计算策略.
  • 增强的数值精度和效率为更复杂的聚合物系统研究铺平了道路.