# Monoclinic crystal system

The Monoclinic crystal system is one of the seven crystal systems in crystallography. It includes all point groups which possess a twofold axis or rotary inversion axis in exactly one direction. This is the only distinguished by a particular direction of symmetry, in this crystal system. The word simply means tilted monoclinic and refers to the two mutually inclined axes with an angle equal to 90 °.

## Point groups

The monoclinic crystal system includes the point groups. They form the monoclinic crystal family and can be described by the monoclinic lattice system.

## Grid system

The monoclinic lattice has the holohedry. In the monoclinic crystal system, the direction of the axis of symmetry plays a special role, it is therefore also called monoclinic axis. This axis also corresponds to a direction of the monoclinic lattice. The other two grid axes are perpendicular to this axis and form an angle equal to 90 °. This angle is also called a monoclinic angle.

For the location of the monoclinic axis, there are two statements:

- The monoclinic axis in the c direction (1st setting ). The monoclinic angle is then γ.
- The monoclinic axis in the b direction ( 2nd setting ). The monoclinic angle β is then.

The 1st setting is now used only rarely. Consequently, the conditions for the monoclinic lattice system ( in the 2nd setting ) arise:

For other details regarding the determination of the directions of the axes other than the axis of the monoclinic, reference is made to the International Tables for Crystallography. The monoclinic lattice system is denoted by m.

## Bravais lattice

In Mono klinai there next to the primitive or a base- centered Bravais lattice. The axes are chosen from Convention so that always results in a c- centering. Deviate from these statements, however, are not uncommon.

## Description and physical properties of the monoclinic point groups

To describe the monoclinic crystal classes in Hermann- Mauguin symbolism symmetry operations with respect to a given direction ( viewing directions ) in the grid system in mono klinai the three viewing directions are the directions of a ( <100 > ), b ( < 010 > ) and c- axis (< 001 > ) of the grid system. If the symbol indicates the directions without symmetry element with the Hermann- Mauguin detailed, these directions are omitted in the abbreviated notation. In this case, can not distinguish between 1st and 2nd one setting.

Characteristic of the Raumgruppensysmbole the monoclinic crystal system is exactly one axis of symmetry with a non-

Wherein the information about the physical properties of "-" means not allowed and " " allowed due to the symmetry due to the symmetry. About the magnitude of the effect can be made due to the symmetry assertion. One can assume that this effect is never exactly disappear.

More monoclinic crystallizing chemical substances, see Category: Monoclinic crystal system