CRYSTAL STRUCTURE

Introduction

Lattice : Structure that is formed by a group of array points on which the basis is attached.

Basis: Atom or groups of atoms which build up the structural attracted to the lattices point.

Crystal : Substance formed by regular repetition in space of atom or groups of atoms.

Crystal structure = Lattice + Basis

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Basis lattice Vector

Shortest displacement vector. (Between 2 lattice point.)

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Unit cell

Symmetry operation

Crystal classification

2-D, 3-D System

Bravais Lattice (BL)

Non-Bravais Lattice (non-BL)

All atoms are of the same kind

All lattice point are equivalent

Atom can be of different kind

Some lattice point are not equivalent

A combination of two or more BL

2D

3D

Primitive

Conventional

Single lattice point per cell

Smallest area in 2D or volume in 3D

More then one lattice point per cell

Integral multiples of the area of primitive cell