Materials Science Exam 1 Vocab

Ionic Bond

A coulombic interatomic bond that exists between two adjacent and oppositely charged ions.

Opposite sides of the periodic table.

Covalent Bond

A primary interatomic bond that is formed by the sharing of electrons between neighboring atoms.

Usually nonmetals.

Metallic Bond

A primary interatomic bond involving the nondirectional sharing of nonlocalized valence electrons ("sea of electrons") that are mutually shared by all the atoms in the metallic solid.

(Only between metals).

Weak/Secondary (Van Der Waals) Bond

A secondary interatomic bond between adjacent molecular dipoles that may be permanent or induced.

Atomic Packing Factor

volume of atoms in unit cell/volume of unit cell

Theoretical Density

Mass of Atoms in Unit Cell/Total Volume of Unit Cell

[(Number of atoms * Molar mass of material)/(Volume of Unit Cell * Avogadro's number)]

Lattice Parameter

Side length of unit cell.

Degree of Polymerization

The number of molecules connected in a chain.

Linear Polymer

A polymer with repeat units joined end to end in a single chain.

Branched Polymer

A polymer having a molecular structure of secondary chains that extend from the primary main chains.

Cross-linked Polymer

A polymer in which adjacent linear molecular chains are joined at various positions by covalent bonds.

Network Polymer (3D)

A polymer produced from multifunctional monomers having three or more active covalent bonds, resulting in the formation of three-dimensional molecules.

Three dimensional interconnected structure.

Point Defect

A crystalline defect associated with one or, at most, several atomic sites.

Vacancy

A normally occupied lattice site from which an atom or ion is missing.

Self interstitial

A host atom or ion positioned on an interstitial lattice site.

Substitutional impurity

A normal lattice site is occupied by a different atom than the rest of the material.

Interstitial impurity

A different atom occupying a position between normal lattice sites.

Frenkel Defect

In an ionic solid, a cation-vacancy and cation-interstitial pair.

Schottky Defect

In an ionic solid, a defect consisting of a cation-vacancy and anion-vacancy pair.

Linear Defect

One-dimensional disorder in a crystalline structure, associated primarily with mechanical deformation.

Edge Dislocation

A linear crystalline defect associated with the lattice distortion produced in the vicinity of the end of an extra half-plane of atoms within a crystal. The Burgers vector is perpendicular to the dislocation line.

Screw Dislocation

A linear crystalline defect associated with the lattice distortion created when normally parallel planes are joined together to form a helical ramp. The Burgers vector is parallel to the dislocation line.