Chemistry of Engineering Materials: Crystal Structures

Crystal

Solid with highly ordered atomic arrangement.

Crystal Systems

Patterns defining the arrangement of crystals.

Lattice Points

Positions of atoms in a crystal structure.

Defect

Missing or misarranged particles in a crystal.

Crystalline Structure

Defined arrangements of molecular chains of atoms.

Noncrystalline Structure

Atoms arranged randomly without periodic order.

Simple Cubic Structure

Unit cell with atoms at cube corners only.

Body-Centered Cubic Structure

Unit cell with atoms at corners and center.

Face-Centered Cubic Structure

Atoms at corners and center of cube faces.

Coordination Number

Number of nearest neighbors around an atom.

Theoretical Density (ρ)

Density calculated from crystal structure parameters.

Atomic Weight (A)

Mass of an atom measured in grams per mole.

Volume of Unit Cell (VC)

Space occupied by a single unit cell.

Avogadro's Number (NA)

6.022 x 10²³ atoms/mol, constant for conversions.

Motif

Group of atoms repeated in a lattice.

Sharp Melting Points

Characteristic of materials with crystalline structure.

Diamonds

Common example of a crystalline solid.

Strontium (Sr)

Element with FCC structure and atomic radius 0.215 nm.

Tantalum (Ta)

Element with BCC structure and atomic weight 180.9 g/mol.

Atomic Radius

Distance from nucleus to outer electron shell.

Density Computation Formula

ρ = nA / (VC * NA) for theoretical density.

Ceramics

Solids with defined atomic arrangements, often brittle.

Polymers

Materials with long molecular chains, often flexible.