Ch 13 - Solids and Modern Materials

Crystalline

Composed of atoms or molecules arranged in structures with long-range order.

Amorphous

Composed of atoms or molecules with no long-range order.

Constructive interference

occurs when two waves interact with their crests and throughs in alignment.

two similar waves combine into a bigger similar wave.

Destructive interference

ocurs when two waves interact with the crets of one aligning with the troughs of the other.

Two different waves combine and cancel eachother.

Bragg’s law

Describes the condition for constructive interference of X-rays scattered by a crystal. It states that nλ = 2d sin(θ), where n is an integer, λ is the wavelength of the X-ray, d is the distance between crystal planes, and θ is the angle of incidence.

Types of cubic unit cell

Simple cubic, Body-Centered Cubic, Face-Centered Cubic

Simple Cubic

A type of cubic unit cell where atoms are located at each of the eight corners of a cube.

Atoms per unit cell - 1

Coordination Number - 6

Edge Length in terms of r - 2r

Packing Efficiency - 52%

Body-Centered Cubic

A type of cubic unit cell where atoms are located at each of the eight corners of the cube and one atom is located at the center of the cube. Atoms per unit cell - 2 Coordination Number - 8 Edge Length in terms of r - 4r/√3 Packing Efficiency - 68%

Face-Centered Cubic

A type of cubic unit cell where atoms are located at each of the eight corners and the center of each face of the cube. Atoms per unit cell - 4. Coordination Number - 12. Edge Length in terms of r - 2√2r. Packing Efficiency - 74%.