Chapter 3: The Structure of Crystalline Solids

Flashcards on the structure of crystalline solids.

refers to the arrangement of atoms or molecules in material

crytal structure

a 3d arrangements of points

lattice concept

3 types of unit cells

FCC, BCC, HCP

anisphysical properties of single crystals of some substance depend on the crystallographic direction

anisotropy

occurs when a wave encounters a series of scattering the wave

diffraction

What does crystal structure refer to?

Arrangement of atoms, ions, and molecules in a material.

What is a crystal lattice?

3D arrangement of points representing atomic positions.

What is a unit cell?

Smallest repeating structure in a crystal.

a form of electromagnetic radiation that has high energy

Xray

Describe a Body-Centered Cubic (BCC) unit cell.

Atoms at corners and one atom at the center

Describe a Hexagonal Close Packed (HCP) unit cell.

Atoms arranged in a hexagonal pattern

Why are unit cells important?

Defines atomic packing, affecting density, strength, and ductility.

What is the atomic packing factor for FCC crystal structure?

0.74

What is the atomic packing factor for BCC crystal structure?

0.68

What is the unit cell edge length for face-centered cubic structures?

a = 2R√2

What is the formula for theoretical density of metals?

ρ = nA / (VcNA)

What are point coordinate indices?

Fractional multiples of unit cell edge lengths.

What is a crystallographic direction?

A line directed between two points, or a vector.

What are Miller indices?

A set of three numbers representing the intercepts of a plane with the crystallographic axes.

How are Miller indices determined?

Reciprocals of the intercepts normalized by lattice parameters.

What is a family of planes?

Equivalent planes having the same atomic packing.

What is the Miller-Bravais system?

A four-axis coordinate system, used for hexagonal crystal structures.

What is a single crystal?

Perfect, repeating arrangement of atoms throughout the specimen.

What are polycrystalline materials?

Collection of many small crystals or grains.

What is anisotropy?

Directionality of properties.

What is isotropy?

Properties are independent of the direction of measurement.

What causes diffraction?

Regularly spaced obstacles scattering a wave.

What is Bragg's Law?

nλ = 2d sinθ