Predicting Crystal Structures in Metals: Is There a Simple Explanation?

In summary, the structure of pure metal elements can be predicted based on the valence shell of the element, with alkali metals tending to have BCC structure and transition metals having FCC or hexagonal closed pack structure. However, these predictions are generalized and there are more detailed calculations involved. These calculations are not based on the 'electron sea' concept, but rather on the symmetry of the s- and d-orbitals. It is unclear if these calculations can explain the structures of alloys or precipitation reactions, and further expertise is needed in this area.
  • #1
scott_alexsk
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Is there any way to predict what crystal structure a pure metal element will be? It seems that the simple 'electron sea' idea does not explain a lot of things.

Thanks
-scott
 
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  • #2
scott_alexsk said:
Is there any way to predict what crystal structure a pure metal element will be? It seems that the simple 'electron sea' idea does not explain a lot of things.

Thanks
-scott

Er.. it actually has nothing to do with the 'elecron sea', at least not directly. It has more to do with the valence shell of the element. Alkali metals, for example, tend to have BCC structure, whereas transition metals tend to have either FCC and hexagonal closed pack. But this really is a rather generalized picture. There's a rather complicated, detailed calculations on why such-and-such a structure is more preferred than others. In fact, in some cases, there can even be a structural phase transition at some temperature or pressure.

Zz.
 
  • #3
So I guess in the case of the alkali metals, since they have fewer valence electrons, they require fewer closest neighbors when forming metallic bonds? For the transition elements, is the same true that since they have a greater number of valence electrons, they require the maximum number of closest neighbors?

Also can these calculations you describe explain the structures of alloys? Can they explain precipitation reactions? Are these calculations based on QM?

Thanks,
-scott
 
  • #4
scott_alexsk said:
So I guess in the case of the alkali metals, since they have fewer valence electrons, they require fewer closest neighbors when forming metallic bonds? For the transition elements, is the same true that since they have a greater number of valence electrons, they require the maximum number of closest neighbors?

Er.. not quite. Remember that alkali metals have an s-orbital as the valence shell. s-orbitals tend to be isotropic. Somehow, this is conducive to forming BCC structures (don't ask me why). Transition metals have d-orbitals as valence shell. So you expect the symmetry of the d-orbitals to dictate how the covalent or metallic bonds form.

Also can these calculations you describe explain the structures of alloys? Can they explain precipitation reactions? Are these calculations based on QM?

Thanks,
-scott

I don't know. Someone else who is an expert in this area needs to come here and help.

Zz.
 

1. What is a crystal structure in metals?

A crystal structure in metals refers to the arrangement of atoms or ions in a repeating pattern. This pattern is known as a crystal lattice and is responsible for the unique properties of metals.

2. How do crystal structures impact the properties of metals?

The crystal structure of a metal influences its mechanical, thermal, electrical, and chemical properties. The arrangement of atoms in the crystal lattice determines factors such as strength, ductility, and conductivity.

3. What are the different types of crystal structures in metals?

The most common crystal structures in metals are face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP). These structures differ in the way atoms are arranged within the crystal lattice.

4. How are crystal structures in metals determined?

Crystal structures in metals can be determined through various techniques such as X-ray diffraction, electron diffraction, and microscopy. These methods allow scientists to visualize and analyze the arrangement of atoms in a crystal lattice.

5. Can the crystal structure of a metal be changed?

Yes, the crystal structure of a metal can be altered through processes such as alloying, heat treatment, and deformation. These methods can change the arrangement of atoms in the crystal lattice and thus alter the properties of the metal.

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