# Crystal system

Set of point groups (a group of geometric symmetries with at least one fixed point).

- Crystal system14 related topics

## Crystal

Solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

Solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

These are grouped into 7 crystal systems, such as cubic crystal system (where the crystals may form cubes or rectangular boxes, such as halite shown at right) or hexagonal crystal system (where the crystals may form hexagons, such as ordinary water ice).

## Crystallography

Experimental science of determining the arrangement of atoms in crystalline solids .

Experimental science of determining the arrangement of atoms in crystalline solids .

Coordinates in angle brackets or chevrons such as <100> denote a family of directions which are related by symmetry operations. In the cubic crystal system for example, would mean or the negative of any of those directions.

## Crystal structure

Description of the ordered arrangement of atoms, ions or molecules in a crystalline material.

Description of the ordered arrangement of atoms, ions or molecules in a crystalline material.

They are similar to, but not quite the same as the seven crystal systems.

## Cubic crystal system

In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube.

## Space group

Symmetry group of an object in space, usually in three dimensions.

Symmetry group of an object in space, usually in three dimensions.

The space groups in three dimensions are made from combinations of the 32 crystallographic point groups with the 14 Bravais lattices, each of the latter belonging to one of 7 lattice systems.

## Bravais lattice

Infinite array of discrete points generated by a set of discrete translation operations described in three dimensional space by:

Infinite array of discrete points generated by a set of discrete translation operations described in three dimensional space by:

In two-dimensional space there are 5 Bravais lattices, grouped into four crystal families, shown in the table below.

## Pyroelectricity

Not to be confused with thermoelectricity, a different thermal effect with a different mechanism.

Not to be confused with thermoelectricity, a different thermal effect with a different mechanism.

All crystal structures belong to one of thirty-two crystal classes based on the number of rotational axes and reflection planes they possess that leave the crystal structure unchanged (point groups).

## Hexagonal crystal family

In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral).

## Monoclinic crystal system

In crystallography, the monoclinic crystal system is one of the seven crystal systems.

## Orthorhombic crystal system

In crystallography, the orthorhombic crystal system is one of the 7 crystal systems.