Crystal structure

The crystal structure describes the arrangement of atoms, ions or molecules in a crystalline material. Given for solid elements under standard conditions in the thermodynamically most stable form. Otherwise, the information refers to the melting point of the element.


The hexagonal unit cell (HEX) describes a hexagonal prism with one atom at each corner. It includes all point groups with a six-fold rotation or rotation inversion axis.

Hexagonal close-packed

Hexagonal close-packed (HCP) unit cells define hexagonal prisms with one atom at each vertex and 3 atoms in the center. It is one of the most common structures for metals.

Body-centered cubic

In the body-centered cubic (BCC) arrangement of atoms, the unit cell consists of eight atoms at the corners of a cube and one atom at the center of the cube.


The rhombohedral unit cell (RHO) is a cube distorted in the direction of the space diagonal. Although it is primitive, it is not conventional, as the threefold axis does not lie in the direction of a lattice vector, but in the direction of the space diagonal.

Simple cubic

The simple cubic unit cell (SC) is the simplest form of the unit cell. Here, there is one atom at each corner of an equilateral cube.

Face-centered cubic

The face-centered cubic unit cell (FCC) defines a cube with one atom at each corner of a cube and on each face.

Diamond structure

The diamond structure (DC) describes the combination of two interpenetrating face-centered cubic lattices that are offset by 1/4 of the space diagonal.


In the orthorhombic lattice system (ORTH), lattice axes lie in the direction of the 3 perpendicular symmetry axes.


The tetragonal crystal system (TETR) includes all point groups that have a fourfold rotation or rotation inversion axis in exactly one direction.

Double hexagonal close-packed

The double hexagonal close-packed (DHCP) crystal structure resembles two regular HCP unit cells stacked on top of each other. This structure is common in several lanthanides and actinides.


The three axes of the unit cell in the monoclinic (MON) crystal system (a, b and c) are unequal. The monoclinic unit has a rectangular shape with a parallelogram as a base.