Test 1 Flashcards
Crystal
Regularly arranged atoms/molecules/ions in a pattern that repeats in multiple dimensions
Lattice
an infinite array of points, the lattice points, each surrounded by an identical environment
Basis
motif that is repeated at each lattice point
Motif
atom/pair of ions/molecules
unit cell
imaginary parallelepiped which can describe the whole of the crystal structure using the simplest possible descriptor
square p-lattice
a=b
y=90
rectangular p-lattice
a not = b
y=90
rectangular c-lattice
a not = b
y=90
hexagonal p-lattice
a=b
y=120
oblique p-lattice
a not =b y not=90
Primitive lattice
have only 1 lattice point inside the unit cell
Centered lattice
have 2 lattice points inside the unit cell (one in the middle and then 1/4 on each side)
cubic lattice
a=b=c, alpha=beta=gamma=90
Tetragonal crystal system
a = b ≠ c
α = β = γ = 90°
Orthorhombic crystal system
a ≠ b ≠ c; α = β = γ = 90°
Monoclinic Crystal System
a≠b≠c
α=γ=90≠β
Triclinic Crystal System
a≠b≠c
α≠β≠γ
one can be 90
Rhombohedral
also known as trigonal
a=b=c
α=β=γ≠90
Hexagonal crystal system
a=b≠c α=β=90 γ=120
Miller planes
aka lattice planes, imaginary planes on which lattice points lie
Simple or Primitive Cube
1 atom per unit cell
coordination number = 6
Body centered cubic (BCC)
2 atoms per unit cell
coordination number = 8
Face centered cubic (FCC)
4 atoms per unit cell
coordination number = 12
hcp
hexagonal close packed ABABAB stacking
octahedral hole
lines between two planar triangle spheres
tetrahedral hole
formed by a planar triangle of touching spheres capped by a single sphere lying in the dip between them
