How do compound objects maintain rigidity despite atomic vibrations?

In summary, the atoms in compound solids vibrate due to thermal energy, but are able to maintain their rigidity through a coupling effect where they vibrate together. This is due to the atoms being in local energy minima and being pushed back to their equilibrium positions. These vibrations are quantized into two types of phonons, acoustic and optical, which are responsible for transmitting sound and have frequencies similar to visible light. However, bending and deforming a solid can introduce defects that disrupt the perfect lattice structure.
  • #1
analyst5
190
2
Hello,

as we all know, in compound solids atoms are always vibrating with some degree, depending on the temperature or the average kinetic energy they posses. My question is how do compound objects maintain their rigidity in those conditions, or to say it better how do atoms stay in fixed positions, or keep fixed distances inside a solid despite their vibrations. It seems as a straight-forward question, but I just wanted to know the details.
 
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  • #2
They don't. The distance between atoms changes as they vibrate.
However it is not clear what you mean by "compound" solids. You mean composed by more than one type of atom?
 
  • #3
Each atomic nucleus sits in a local minimum of potential energy. Therefore there is always a force that pushes it back to the equilibrium position when it moves away, e.g. due to thermal vibrations.

In a real solid, the atoms are not independent. Instead they are coupled, like a chain of balls with springs in between them. The result is that they all vibrate together. The phase between their oscillations leads to a wave-like motion. Because all this happens at the atomic level these motions are quantized - they are called phonons.

There are two basic types of phonons: with a small phase between the atoms they are called acoustic photons (because they are responsible for transmitting sound through the solid), and if they are nearly out of phase they are called optical phonons (because the frequencies are near those of visible light). Well, that's hand waving, the details are a bit more complicated.

http://en.wikipedia.org/wiki/Phonon

Bending and plastically deforming a material is yet another story. When you do that you introduce all kinds of defects into the crystal lattice that break the perfect translation symmetry.
 

FAQ: How do compound objects maintain rigidity despite atomic vibrations?

1. What is rigidity?

Rigidity refers to the stiffness or resistance to deformation of a material. It is a measure of how much a material can withstand external forces without changing its shape or size.

2. What are atomic vibrations?

Atomic vibrations are the periodic movement of atoms in a material due to thermal energy. Atoms vibrate around their equilibrium positions, and the amplitude and frequency of these vibrations can affect the material's properties, such as rigidity.

3. How does rigidity relate to atomic vibrations?

Rigidity and atomic vibrations are closely related. The stiffness of a material depends on the strength of the bonds between its atoms, which is influenced by atomic vibrations. A material with stronger bonds and less atomic vibration will be more rigid, while a material with weaker bonds and more atomic vibration will be less rigid.

4. Can rigidity be changed by altering atomic vibrations?

Yes, rigidity can be changed by altering atomic vibrations. By increasing or decreasing the amplitude and frequency of atomic vibrations, the strength of the bonds between atoms can be affected, thus changing the material's rigidity.

5. What are some real-world applications of understanding the relationship between rigidity and atomic vibrations?

Understanding the relationship between rigidity and atomic vibrations is crucial in material science, engineering, and nanotechnology. It can help in designing and developing materials with specific properties, such as high rigidity for building structures or low rigidity for flexible electronics. It can also aid in predicting the behavior of materials under different conditions, such as temperature changes or external forces.

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