P63/mmc (3 is actually a subscript letter), is type of HCP crystal structure, where:

- P stands for primitive Bravais lattice

- 6 stands for hexagonal (or the screw lattice, where angles are equal to 360/n ; when n is equal to 6 it is hexagonal, but when it is 4 it is tetragonal (angles are 90) for example)

- 3 is denoting the chirality

- mmc are the Herman-Mauguin symbols

If you include "space group" in your searches you will find more information. It's the international short symbol notation, where the letters and numbers refer to the lattice and symmetries. If interested, you can also search for Wyckoff positions, which is a way to define the atom positions using the symmetries for the space group. The space group you mentioned is number 194 going by the International Union of Crystallography. Here's a wikipedia entry to get you started:

http://en.wikipedia.org/wiki/Space_group

P63/mmc (3 is actually a subscript letter), is type of HCP crystal structure, where:

- P stands for primitive Bravais lattice

- 6 stands for hexagonal (or the screw lattice, where angles are equal to 360/n ; when n is equal to 6 it is hexagonal, but when it is 4 it is tetragonal (angles are 90) for example)

- 3 is denoting the chirality

- mmc are the Herman-Mauguin symbols

HCP (meaning hexagonal closed pack) is a broad class of crystallographic structure. The exact crystal structure is denoted by "Space group" like P63/mmc in your case. x Information about the Bravais lattice, Wyckoff positions (atomic positions), symmetries etc are summarized in"space group".

Check out: http://en.wikipedia.org/wiki/Hexagonal_crystal_system

Thanks to all. Special thanks to Elbay Malikmammadov. I just needed the things that we have answered. Thank you so much.

Mr. Soud, your question was not silly for me either. The answers helped me too. Thank you all.

P63/mmc

is the International notation or Hermann-Mauguin notation to identify the crystal structure and symmetries involved.

P is the primitive or pristine Bravais lattice

6 is assigned for hexagonal crystal system, where rotational symmetry or angle of rotation =360/6 =60 deg

subscript 3 indicates the chiral symmetry

1st m is the mirror plane perpendicular to the c-axis

2nd m is the mirror plane parallel to the c-axis, and

c stands for glide planes

space group 194 tell the secret of many fasional materials, such as graphene and MXene....