Iris
FCCFace-Centered Cubic
Atoms: --   Bonds: --
Crystal Structure
Display Options
Atom Size 1.0
Zoom 1.0
Coordination #
12
Packing Fraction
74.05%
Atoms per Cell
4

Crystal Structures

Crystalline solids arrange their atoms in periodic lattice patterns. The unit cell is the smallest repeating unit that tiles to fill all space. Different arrangements yield different physical properties: density, strength, ductility.

Common Structures

Simple Cubic (SC) has atoms only at corners — the least efficient packing (52%). BCC adds a center atom (68% packing, found in iron and tungsten). FCC and HCP both achieve the theoretical maximum packing of 74% (aluminum, copper, gold for FCC; titanium, zinc for HCP). Diamond Cubic has just 34% packing but each atom has exactly 4 neighbors in a tetrahedral arrangement (carbon, silicon, germanium).

Coordination Number

The coordination number is the count of nearest neighbors for each atom. SC: 6, BCC: 8, FCC: 12, HCP: 12, Diamond: 4. Higher coordination generally means denser, more metallic bonding.