《固体物理学》课程教学课件（PPT讲稿）Chapter 1 Crystal Structure 1.1 Elementary Crystallography 1.2 Crystal Structure ≡ Lattice + Basis 1.3 Lattice Translation Vectors 1.4 Non-Bravais Lattices 1.5 Wigner-Seitz Method

Chapter 1:Crystal Structure Objectives At the end of this Chapter,you should: 1.Be able to identify a unit cell in a symmetrical pattern. 2.Know that there are7 Possible unit cell shapes. 3.Be able to define cubic,tetragonal,orthorhombic hexagonal unit cell shapes. 4.Know how to index the crystal plane and the crystal direction. 5.Understand the difference between complex lattice and simple lattice 6.Understand the symmetry elements

Objectives At the end of this Chapter, you should: 1.Be able to identify a unit cell in a symmetrical pattern. 2. Know that there are7 Possible unit cell shapes. 3. Be able to define cubic, tetragonal, orthorhombic & hexagonal unit cell shapes. 4. Know how to index the crystal plane and the crystal direction. 5.Understand the difference between complex lattice and simple lattice 6. Understand the symmetry elements Chapter 1: Crystal Structure

The (Common)Phases of Matter MATTER LIQUIDS GASES AND LIQUID SOLIDS CRYSTALS This doesn't include Plasmas,but these are the“common”phases! “Condensed Matter”includes both ofthese.We'll focus on Solids!

The (Common) Phases of Matter Matter GASES LIQUIDS and LIQUID CRYSTALS SOLIDS “Condensed Matter” includes both of these. We’ll focus on Solids! This doesn’t include Plasmas, but these are the “common” phases!!

1.1 Elementary Crystallography Solid Material Types Crystalline Polycrystalline Amorphous (Non-Crystalline) Single Crystal

1.1 Elementary Crystallography Solid Material Types Crystalline Polycrystalline Amorphous (Non-Crystalline) Single Crystal

Single Crystal A Single Crystal has an atomic structure that repeats periodically across its whole volume.Even at infinite length scales,each atom is related to every other equivalent atom in the structure by translational symmetry. Single Crystals Single Pyrite Amorphous Crystal Solid

A Single Crystal has an atomic structure that repeats periodically across its whole volume. Even at infinite length scales, each atom is related to every other equivalent atom in the structure by translational symmetry. Single Crystals Single Pyrite Crystal Amorphous Solid Single Crystal

Polycrystalline Solids A Polycrystalline Solid is made up of an aggregate of many small single crystals have a high degree of order over many atomic or molecular dimensions,vary in size orientation with respect to one another.These regions are called grains (or domains) are separated from one another by grain boundaries. Polycrystals with grains that are 10 nm in diameter are called nanocrystallites Grain Boundaries (Differently red Crystals)

Polycrystalline Solids A Polycrystalline Solid is made up of an aggregate of many small single crystals , have a high degree of order over many atomic or molecular dimensions, vary in size & orientation with respect to one another. These regions are called grains (or domains) & are separated from one another by grain boundaries. Polycrystals with grains that are < 10 nm in diameter are called nanocrystallites

Amorphous Solids Amorphous (Non-crystalline)Solids are composed of randomly orientated atoms,ions,or molecules that do not form defined patterns or lattice structures.Amorphous materials have order only within a few atomic or molecular dimensions.They do not have any long-range order,but they have varying degrees of short-range order.Examples of amorphous material include amorphous silicon,plastics, glasses

Amorphous Solids • Amorphous (Non-crystalline) Solids are composed of randomly orientated atoms, ions, or molecules that do not form defined patterns or lattice structures. Amorphous materials have order only within a few atomic or molecular dimensions. They do not have any long-range order, but they have varying degrees of short-range order. Examples of amorphous material include amorphous silicon, plastics, & glasses

1.2 Crystal Structure Lattice Basis Lattice:arranging way Basis:group of atoms arranged Crystal ● ● ● ● ，● ● ●】 ●● ● ●● ●● Basis Lattice=Crystal

• Lattice: arranging way • Basis: group of atoms arranged 1.2 Crystal Structure ≡ Lattice + Basis

A Two-Dimensional Bravais Lattice with Different Choices for the Basis Bravais basis crystal lattice ●

A Two-Dimensional Bravais Lattice with Different Choices for the Basis

Crystal Structure Lattice Basis Basis The atoms do not necessarily lie at lattice points!!

9 Crystal Structure = Lattice + Basis Basis  The atoms do not necessarily lie at lattice points!!

The primitive cell selection of 2D square lattices

The primitive cell selection of 2D square lattices