Quiz 1 Basic Materials

Body Center Cubic BCC

-2 atoms in the unit cell -Volume is a^3

Face Center Cubic FCC

-4 atoms -volume is a^3

Hexagonal Closed Packed HCP

-a=2R -6 atoms -V=((3•3^½)/2)a^2•c

Miller indices

A set of three integers (four for hexagonal) that designate crystallographic planes, as determined from reciprocals of fractional axial intercepts.

Long Range Order

A solid is crystalline if it has long-range order. Once the positions of an atom and its neighbours are known at one point, the place of each atom is known precisely throughout the crystal. Most liquids lack long-range order, although many have short-range order.

Linear Packing Factor

AFP= (Natoms)(Vatoms)/(Vcrystal)

Crystallic Directions

Crystal directions are directions relative to a crystal reference frame and are usually defined in terms of Miller indices.

Polycrystalline

Crystalline materials composed of more than one crystal or grain.

Anisotropic

Exhibiting different values of a property in different crystallographic directions.

Crystal Structure

For crystalline materials, the manner in which atoms or ions are arrayed in space. It is defined in terms of the unit cell geometry and the atom positions within the unit cell.

Isotropic

Having identical values of a property in all crystallographic directions. long range order

interstices

Holes or void spaces in the crystal

Amorphous

In condensed matter physics and materials science, an amorphous (from the Greek a, without, morphé, shape, form) or non-crystalline solid is a solid that lacks the long-range order that is characteristic of a crystal.

Lattice points

Lattice points are the positions (or coordinates if you wish) where you can place an atom. Therefore you can find either atoms or vacancies in the lattice points of a crystal structure

Primitive Unit Cell

Primitive unit cells contain only one lattice point, which is made up from the lattice points at each of the corners. Non-primitive unit cells contain additional lattice points, either on a face of the unit cell or within the unit cell, and so have more than one lattice point per unit cell.

Short Range Order

Short range is defined as the first- or second-nearest neighbours of an atom. In many liquids the first-neighbour atoms are arranged in the same structure as in the corresponding solid phase.

Bravais Lattices

The Bravais lattice are the distinct lattice types which when repeated can fill the whole space. The lattice can therefore be generated by three unit vectors, a1, a2 and a3 and a set of integers k, l and m so that each lattice point, identified by a vector r, can be obtained from: r = k a1 + l a2 + m a3

Polymorphism crystal structure

The ability of a solid material to exist in more than one form or crystal structure. can change dimensions based on things like heat

Unit Cell

The basic structural unit of a crystal structure. It is generally defined in terms of atom (or ion) positions within a parallelepiped volume.

Lattice Parameters

The combination of unit cell edge lengths and interaxial angles that defines the unit cell geometry.

Lattice Constants

The lattice constant, or lattice parameter, refers to the physical dimension of unit cells in a crystal lattice. Lattices in three dimensions generally have three lattice constants, referred to as a, b, and c. However, in the special case of cubic crystal structures, all of the constants are equal and we only refer to a. Similarly, in hexagonal crystal structures, the a and b constants are equal, and we only refer to the a and c constants. A group of lattice constants could be referred to as lattice parameters

Motif

The motif is a list of the atoms associated with each lattice point, along with their fractional coordinates relative to the lattice point.

Coordination Number

The number of atomic or ionic nearest neighbors.

Planar Packing Factor

The planar packing fraction = (area in plane occupied by the atoms) / (area of plane) (#atoms)(pi(r)^2)/(area of plane)

Lattice

The regular geometrical arrangement of points in crystal space.

Volume of an atom

V=(4/3)pi(r)^3

Basis

what the atom is made up of, like the atoms themself.