6&7. Crystal Structure Flashcards
Which classes of material do crystalline structures occur in
Metals, many ceramics and certain polymers
Define crystalline material
A material in which atoms are arranged in a repeating array, and exhibit long-range order
Define crystal structure
the spatial arrangement of atoms in crystalline solids
Define crystal morphology
the shape and size of crystals or grains
Define unit cell
the repeating entity that defines the structure in a crystalline solid
What does FCC stand for?
Face centered cubic
What does BCC stand for?
Body centered cubic
What does HCP stand for?
Hexagonal close packed
What does HCP stand for?
Hexagonal close packed
Define coordination number
The number of nearest- neighbor or touching atoms in a crystal structure
define close packed directions
The directions within the unit cell with highest linear density of atoms
Define atomic packing factor
volume of atoms in a unit cell per volume of a unit cell
Do substances always maintain the same crystal structure?
Not always. Some metals/non-metals have more than one stable crystal structure. (eg. Iron changes from BCC to FCC to BCC again as temperature increases)
Do different crystal structures for the same material have the same properties?
No, each crystal structure will have different mechanical, thermal, and electrical properties
Which has a higher packing density BCC or FCC? (For the same atoms)
FCC
