Exam 1

Crystal
3-D Periodic array of atoms.
Crystallinity
Long range order and periodicity of atoms.
Ideal Crystal
An infinite regular repetition in space of identical structural untis
Basis / Motif
Group of atoms, ions, or molecules associated with each lattice point.
Lattice
A regular periodic arrangement of points in space.
Crystal Structure
Basis plus Lattice
Unit Cell
A small repetitive volume that forms the complete lattice
Lattice Constants
Dimensions of the unit cell
Lattice Parameter
Dimensions of the unit cell and the associated angles between the axes
Lattice Coefficients
Lattice constants expressed in unit cell dimensions
Primitive Cell
Parallelpiped defined by primitive axes
Equivalent Site
Lattice sites with fully identical surroundings
Coordination Number
Number of nearest neighbors
Amorphous Material
Material lacking long-range order, glassy
Polymorphism
A material that can exist in more than one crystalline form
Allotropy
Another name for Polymorphism
Crystal system
scheme by which crystals are classified according to unit cell geometry
Miller Indicies
Set of three integers that designate crystallographic planes
Atomic Packing Factor
The fraction of space filled by atoms within a particular crystal structure