Are the properties of a crystal and its unit cell same?

  • #1
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1) My teacher said that to analyze the properties of entire crystalline solid, we just need to analyze the properties of a unit cell, which is the smallest repeating unit of a crystalline solid.

2) But crystalline solids are known to be anisotropic, i.e. they have different properties in different directions.

Are not these two statements contradicting?
 

Answers and Replies

  • #2
516
63
1) My teacher said that to analyze the properties of entire crystalline solid, we just need to analyze the properties of a unit cell, which is the smallest repeating unit of a crystalline solid.

2) But crystalline solids are known to be anisotropic, i.e. they have different properties in different directions.

Are not these two statements contradicting?
The unit cell can be anisotropic, look at the tetragonal crystal structure for instance, the c axis is stretched relative to the a and b axes. Typically undergraduate courses only ever deal with cubic lattices, as they are easier to solve, but there are many other structures, with different symmetries.
Equally you can have an orthorombic crystal, where one of the angles is not 90 degrees.
 
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