一、Crysta Lattice

Crystal: Atoms arranged in a three-dimensional space in a long order; Cell: The smallest unit of repeated arrangement called cell cell cell parameters: three axis length a,b,c three axis Angle a,P,Y according to the arrangement law can be divided into 7 kinds of crystal systems, 14 kinds of lattice, 230 kinds of space groups. Most kinds of matter are crystals.

二、Crystal face、 Crystal direction

1. A crystallographic plane is formed by three nodes of a lattice that are not in a straight line, referred to as the crystal face. The vertical distance between two adjacent individual planes is called the crystal plane spacing. The crystal face is based on the crystal face index (hkI means that the plane closest to the origin and the b,c triaxial intersect at a/hb/kc/ that group of crystal faces is (hkI) crystal face, h,k1 should be an integer, and the crystal face index is also known as the Miller index.

2. As shown on the left，crystal direction refers to a group of parallel vectors, not referring to the vector passing through a node, starting from the origin, if the coordinates of the nearest lattice with integer coordinates passing along the direction of the vector are uyw, then the crystal direction is defined as [uvp] product direction. u,yw can be negative. Hexagonal indices can be expressed in two ways: three-exponent and four-exponent, such as (110) and (1120).

                      China X-ray Powder Diffractometer