Crystallography Flashcards
What is the form of a crystallographic point? Direction? Family of directions? Plane? Family of Planes?
Point : # # #
Direction : [# # #]
Family of directions:
Plane : (# # #)
Family of planes: {# # #}Define equivalent directions.
Directions that have the same spacing of atoms.
Define a family of directions
Directions with the same numbers, regardless of sign or sequence. Cubic families are equivalent.
Why is crystallographic direction important?
Material properties differ depending on direction.
Define linear density.
LD = # of atoms centered on direction / length of direction
Define a single crystal.
A crystal where all of the unit cells are aligned. (no grains.)
Define a polycrystal.
A crystal where unit cells change directions. (grains)
Define grain boundary.
Area where two grains meet.
Define Isotrophy
Same properties in all directions.
Define Anisotrophy.
Different properties in different directions.
Are single crystals anisorophic or isotrophic. Polycrystals?
Single crystals are anisotrophic. Polycrystals are usually isotrophic, unless grains are oriented in the same direction.
How are planes and directions that have the same form related?
eg {1 2 3} (1 2 3)
They are perpendicular
Define planar density
PD = # of atoms centered on plane / area of plane
Define the planar packing fraction
PPF = percent of plane covered by atoms
Define interplanar spacing
The distance between two parallel planes in a structure.
For cubics, d = a/sqrt(u^2 + v^2 + w^2)
