Crystallography

Question 1

What is a lattice

Answer 1

A lattice is a series of points that are arranged in a distinct pattern. A crystal lattice structure is similar to a lattice, but instead of points, it is composed of a series of atoms.

Question 2

Unit cell

Answer 2

The smallest unit that describes the symmetry and distribution of the lattice

Question 3

Motif

Answer 3

Atomic arrangement in each unit cell

Question 4

Structure

Answer 4

Lattice + Motif

Question 5

5 2D Lattice types

Answer 5

Primitive Square Lattice
Regular Primitive Lattice
Oblique Primitive Lattice
Rectangular Centered Lattice
Hexagonal Primitive Lattice

Question 6

Glide plane

Answer 6

Mirror + Translation

Question 7

4 types of Rotational symmetry

Answer 7

2 fold/Diad
3 fold/Triad
4 fold/Tetrad
6 fold/Hexad

Question 8

3 rules of a unit cell

Answer 8

Same symmetry
Edges coincide
Smallest that corresponds

Question 9

7 Crystal Systems + Angle + Faces

Answer 9

Cubic a=b=c / a1=a2=a3  α=β=γ=90°    
Tetragonal a=b≠c / a1=a2≠c  α=β=γ=90°
Orthorhombic a≠b≠c α=β=γ=90°
Monoclinic  a≠b≠c α=γ=90°  β≠90°
Triclinic  a≠b≠c α≠β≠γ≠90°
Triagonal  a1=a2=a3≠c α=β=90° γ=120°
Hexagonal a1=a2=a3≠c α=β=90° γ=120°

Question 10

14 Bravais Lattices

Answer 10

Cubic-> Primitive, Body Centered (bcc), Face Centered (fcc)
Tetragonal-> Primitive, Body Centered
Orthorhombic-> Primitive, Body-Centered, Face Centered, ‘c’ Centered
Monoclinic-> Primitive, ‘c’ Centered
Triclinic-> Primitive
Triagonal-> Primitive
Hexagonal-> Primitive

Question 11

3 Types of Crystal Symmetry

Answer 11

Planar/Mirror-> Each side of the plane is a mirror of the other
Axial/Rotational -> the Same position reached how many times in the rotation of the axis
Centers of Symmetry -> Same faces on opposite sides

Question 12

Miller Indicies

Answer 12

The system of crystallographic indexing for crystal faces. If it never crosses an axis the value is 0, if it crosses at the full length it is 1 and if it crosses at half it is 2 and so on. If it is negative then there is a bar over it. It is given in the format (hkl) or (hkil).