Chapther 1 crystal structures Flashcards
What are the two types of interstitial sites in cp structures?
Tetrahedral and Octahedral
How many orientations of tetrahedral sites are present in ccp structures?
Four equivalent orientations
What characterizes octahedral sites in crystal structures?
Coordinated to three anions in each layer, located midway between layers
What symmetry operation combines rotation and inversion?
Inversion axis
Which inversion axes are possible in crystals?
¯1, ¯2, ¯3, ¯4, and ¯6
What does the unit cell specification include?
Size, shape, and atomic coordinates
How is a primitive unit cell characterized?
Lattice points only at the corners
What is an example of a face centered cubic (fcc) structure?
Copper (Cu)
How are body centered cubic (bcc) structures distinguished?
They have an extra lattice point at the body center
What do lattice planes reference in crystal structures?
Imaginary planes providing a grid for atomic arrangement
What defines the interplanar d-spacing?
Distance between pairs of adjacent lattice planes
What is a common characteristic of NaCl’s crystal structure?
It is face centered cubic (fcc) and has Z = 4
What does the term ‘coordination number’ refer to?
The number of closest neighboring atoms surrounding an atom
What are the limitations of close packing models?
They cannot apply to all types of structures
Why might unit cells alone not be sufficient to describe a crystal?
They don’t provide a full 3D representation of the structure
