Video Experimental Relacionado

Updated: Jul 9, 2026

Quantitative Atomic-Site Analysis of Functional Dopants/Point Defects in Crystalline Materials by Electron-Channeling-Enhanced Microanalysis

Quantitative Atomic-Site Analysis of Functional Dopants/Point Defects in Crystalline Materials by Electron-Channeling-Enhanced Microanalysis

Published on: May 10, 2021

Observación directa de un mecanismo vibratorio transversal para la expansión térmica negativa en Zn(CN) 2: un

Karena W Chapman¹, Peter J Chupas, Cameron J Kepert

¹School of Chemistry, University of Sydney, Sydney, NSW 2006 Australia.

Journal of the American Chemical Society

|November 3, 2005

Resumen

La expansión térmica negativa (NTE) en Zn(CN) 2 es causada por el aumento del desplazamiento transversal de los puentes de cianuro. Esta visión estructural explica el NTE a pesar de la expansión de los bonos individuales.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Química del estado sólido.
La cristalografía es una técnica de cristalografía.

Sus antecedentes:

Los materiales de expansión térmica negativa (NTE) exhiben propiedades únicas.
Comprender los mecanismos de NTE a nivel atómico es crucial para el diseño de materiales.
El cianuro de zinc (Zn(CN) 2) es un material NTE conocido con una estructura de marco compleja.

Objetivo del estudio:

Para investigar la estructura atómica instantánea de Zn(CN) 2.
Para dilucidar el origen microscópico de la expansión térmica negativa en Zn(CN) 2.
Para correlacionar la dinámica estructural con el comportamiento macroscópico de expansión térmica.

Principales métodos:

Análisis de la función de distribución de pares atómicos (PDF). análisis.
Experimentos de dispersión de rayos X de alta energía.
Análisis estructural dependiente de la temperatura (100-400 K).

Principales resultados:

El análisis de PDF reveló un aumento del desplazamiento transversal de los puentes de cianuro con el aumento de la temperatura.
Este desplazamiento permite la contracción de las distancias no-vecina más cercana (Zn...Zn', Zn...C/N).
Se observó que las longitudes de los bonos individuales (Zn-C/N, C-N) se expandieron.

Conclusiones:

El estudio confirma que el aumento del desplazamiento promedio de los átomos puentes es el origen de la NTE en Zn (CN) 2.
Una ligera reducción de NTE a temperaturas más altas se atribuye a las interacciones de marco interpenetrado.
Se proporcionaron pruebas estructurales definitivas para el mecanismo de NTE en Zn(CN) 2.

Más Videos Relacionados

Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry

Thermochemical Studies of Ni(II) and Zn(II) Ternary Complexes Using Ion Mobility-Mass Spectrometry

Published on: June 8, 2022

High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements

High-Speed Magnetic Tweezers for Nanomechanical Measurements on Force-Sensitive Elements

Published on: May 12, 2023

Videos de Conceptos Relacionados

Atomic Nuclei: Nuclear Spin State Overview

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: Nuclear Spin State Population Distribution

Atomic Nuclei: Nuclear Spin State Population Distribution

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.

Atomic Nuclei: Nuclear Relaxation Processes

Atomic Nuclei: Nuclear Relaxation Processes

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. This...

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.

IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration

IR Spectroscopy: Hooke's Law Approximation of Molecular Vibration

A covalently bonded heteronuclear diatomic molecule can be modeled as two vibrating masses connected by a spring. The vibrational frequency of the bond can be expressed using an equation derived from Hooke's law, which describes how the force applied to stretch or compress a spring is proportional to the displacement of the spring. In this case, the atoms behave like masses, and the bond acts like a spring.
According to Hooke's law, the vibrational frequency is directly proportional to the...