Crystal Structure: Properties of Materials Depend on Structure

In summary, the properties of materials, including density, thermophysical and mechanical properties, are greatly influenced by the crystal structure of the material. The interatomic spacing and symmetry of the crystal structure affect properties such as thermal conductivity, strength, and isotropy. The orientation and presence of defects in the crystal structure also play a role in determining properties. Additionally, thermodynamic, electronic, and magnetic properties are related to crystal structure, as seen in examples such as superconductors and long afterglow phosphors. Overall, the crystal structure is a crucial factor in understanding and predicting the properties of materials.
  • #1
mecheng
12
0
Which properties of materials depend on the crystal structure (f.c.c., b.c.c. cph etc...) of materials?
 
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  • #2
mecheng,

How about density? :-)
 
  • #3
Probably all thermophysical and mechanical properties depend to some degree (some more so than others) on crystal structure (morphology), but then each element which is solid has a preferred crystal structure.

Interatomic spacing, as well as the inherent attraction between the atoms, affects properties like thermal conductivity and strength.

Cubic structures are more isotropic due to symmetry. Crystals which are elongated in one or two of three directions exhibit anisotropies in their properties, i.e. the properties have a directional dependence.

Hexagonal close-packed metals (e.g. Zr) have a property called 'texture' which relates to the fraction of grains with a particular orientation of the basal poles, or c-axis (normal to the basal plane) in a poly-crystalline phase.

Most metals are found in a poly-crystalline as opposed to single-crystal structure. And within either configuration, some dislocations or holes in the lattice may occur. These too have important implications with respect to properties.
 
  • #4
mecheng said:
Which properties of materials depend on the crystal structure (f.c.c., b.c.c. cph etc...) of materials?

Virtually all of them do.

Ductility is clearly related to the existence of slip planes. The FCC structure has slip planes along (111) directions, while the BCC crystal's slip planes are the (110) family. This difference is instrumental in determining the plastic flow characteristics of the material. As a result, Cu, Ag, Au (all FCC metals) are extremely ductile, while Fe, Ni (BCC) are not. Hardness is inversely related to ductility and so hardness trends follow likewise. Tensile strength and toughness are also related to crystal structure, but other factors (microstructure, heat treatment, alloying) often dominate.
 
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  • #5
Also, thermodynamic, electronic and magnetic properties are related to crystal structure.

In the High Tc Cuprites, the Cu-O planes are vital to the incidence of superconductivity. In CMR manganites, the O-Mn-O bond angle affects the MR ratio. In aluminate-based long afterglow phosphors, there is a strong correlation between the lattice parameter and the wavelength of emitted light. Mobility of semiconductors, conductivity of diamond, magnetic anisotropy in transition metal-rare Earth intermetallics, etc. are all heavily dependant on the crystal structure.
 
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1. What is crystal structure?

Crystal structure refers to the arrangement of atoms or molecules in a solid material, which can be visualized as a repeating pattern in three dimensions. It determines many of the physical and chemical properties of a material, such as its strength, density, and conductivity.

2. How does crystal structure affect material properties?

The specific arrangement of atoms or molecules in a crystal structure influences the way the material behaves and interacts with its surroundings. For example, a material with a tightly packed crystal structure will be stronger and more dense compared to a material with a more loosely packed crystal structure.

3. Can crystal structure be altered?

Yes, crystal structure can be altered through various processes such as heating, cooling, and applying pressure. These changes in crystal structure can result in different material properties, which is why materials can have different properties even if they are made of the same elements.

4. How do scientists determine the crystal structure of a material?

Scientists use various techniques such as X-ray diffraction, electron microscopy, and spectroscopy to determine the crystal structure of a material. These methods allow them to analyze the atomic arrangement and identify the type of crystal lattice present in the material.

5. Why is understanding crystal structure important in materials science?

Understanding crystal structure is crucial in materials science because it helps scientists predict and control the properties of a material. By manipulating the crystal structure, scientists can create materials with specific properties that are useful in various applications such as electronics, construction, and medicine.

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