Material Science - Atomic Structure and Crystalline Systems (EMB 5022)

Vocabulary flashcards covering the fundamentals of atomic structure, chemical bonding, and crystallography based on the EMB 5022 Exercise List.

Atomic Structure

The arrangement of atoms and their subatomic constituents, which include protons, neutrons, and electrons.

Diamond vs. Polyethylene Melting Points

Carbon atoms in diamond are held by strong 3D covalent networks resulting in a high melting point, whereas polyethylene consists of polymer chains held by weak Van der Waals forces, leading to a much lower melting point.

Ceramic Chemical Bonding

Predominantly ionic or covalent bonds; these strong bonds define properties such as high hardness, high melting points, and electrical insulation.

Primary Chemical Bonds

The three main types of strong interatomic bonds: ionic, covalent, and metallic.

Melting Temperature / Thermal Expansion Relationship

In metals, there is an inverse relationship; materials with a high melting temperature typically possess a low coefficient of thermal expansion due to stronger interatomic bonding.

Crystalline Structure

The periodic and repeating spatial arrangement of atoms, ions, or molecules in a solid material.

Unit Cell

The smallest repeating entity of a crystalline structure that represents the symmetry and geometric arrangement of the entire lattice.

Allotropy

The ability of a material to exist in more than one crystalline form or structure depending on temperature and pressure.

CCC to CFC Transformation Geometry

An allotropic transformation from Body-Centered Cubic ($CCC$ or $BCC$) to Face-Centered Cubic ($CFC$ or $FCC$) results in a volume contraction because the atomic packing factor increases from $0.68$ to $0.74$.

Amorphous Solid vs. Liquid

Amorphous solids possess short-range order but lack the long-range periodicity of crystals, whereas liquids lack both long-range order and structural rigidity.

CCC (Body-Centered Cubic)

A crystalline structure with $2$ atoms per unit cell, a coordination number of $8$, and an atomic packing factor (APF) of $0.68$.

CFC (Face-Centered Cubic)

A crystalline structure with $4$ atoms per unit cell, a coordination number of $12$, and an atomic packing factor (APF) of $0.74$.

HC (Hexagonal Close-Packed)

A crystalline structure with $6$ atoms per unit cell, a coordination number of $12$, and an atomic packing factor (APF) of $0.74$.

Crystal Systems

There are $7$ systems (Cubic, Tetragonal, Orthorhombic, Hexagonal, Monoclinic, Triclinic, and Rhombohedral) categorized by their unit cell geometry (axial lengths and interaxial angles).