Mse Ch 3

Front 1

allotropic

Back 1

capable of having more than one crystal structure

Front 2

anisotropic

Back 2

Having properties that vary with direction

Front 3

atomic packing factor (APF)

Back 3

The fraction of space in a unit cell filled by spherical atoms.

Front 4

basal plane

Back 4

The top or bottom plane in a crystal. In hexagonal crystals the basal plane is defined by the atoms placed on the six corners of hexagons. It is normal to the c axis.

Front 5

basis

Back 5

The number of atoms or ions on each lattice position

Front 6

body-centered cubic (BCC)

Back 6

A cubic structure in which atoms are located in the corners of the unit cell plus one in the center of the cubic unit cell

Front 7

Bragg's law

Back 7

The defining equation of X-ray diffraction, n = 2d sin .

Front 8

close-packed direction

Back 8

A crystallographic direction in a crystal along which atoms touch.

Front 9

close-packed plane

Back 9

A crystallographic plane in a crystal on which each atom contacts six neighbors.

Front 10

close-packed structures

Back 10

A crystal of a single atom type in which the spherical atoms are packed as tightly as possible, giving a coordination number of l2 and an APF of 0.74. ex. HCP and FCC

Front 11

coordination number

Back 11

The number of nearest neighbors that surround an atom or ion

Front 12

crystal lattice

Back 12

The framework on which atoms are placed in periodic three-dimensional structures.

Front 13

diffraction

Back 13

A specific interaction of radiation with materials. appears as reflections from parallel planes and is governed by Bragg's law

Front 14

face-centered cubic (FCC)

Back 14

A cubic crystal in which the atoms or ions are positioned at each corner and in the center of each of the six faces

Front 15

families of directions

Back 15

All the equivalent directions in a crystal, which are all the permutations of the Miller indices of any direction in the family

Front 16

families of planes

Back 16

All the equivalent planes in a crystal, which are all the permutations of the Miller indices of any plane in the family

Front 17

hexagonal close-packed (HCP)

Back 17

A crystal that has a regular hexagonal basal plane and rectangular side planes normal to the basal plane. Individual atoms or ions are located at each corner of the basal plane and in the center of the basal plane, and three more atoms are on the midplane, located over the interstices of the atoms in the basal plane. Each atom has 12 neighbors that touch, giving an APF of 0.74.

Front 18

highest-density plane

Back 18

A crystallographic plane with the largest number of atoms or ions centered on the plane per unit area

Front 19

interstices

Back 19

The regions between atoms that are defined by at least four atoms or ions. Interstices in crystals are usually tetrahedral or octahedral

Front 20

lattice

Back 20

Three-dimensional space-filling repeating pattern on which atoms or ions are placed to form a crystal.

Front 21

lattice parameter

Back 21

The lengths of the unit-cell edges.

Front 22

lattice point

Back 22

One position in the three-dimensional space-filling repeating pattern that forms a crystal. One or more atoms or ions are placed at each lattice point

Front 23

linear density

Back 23

The number of atoms centered on a crystallographic direction per unit length.

Front 24

liquid crystal

Back 24

An anisotropic fluid, usually a melt or solution characterized by molecular alignment.

Front 25

Miller indices

Back 25

A shorthand for expressing directions and planes in crystals

Front 26

octahedral site

Back 26

A position in a crystal defined by six nearest neighbors

Front 27

planar density

Back 27

The number of atoms or ions centered on a crystallographic plane per unit area of the plane.

Front 28

polycrystalline

Back 28

Describing a solid, usually isotropic, of joined crystals or grains.

Front 29

polymorphic

Back 29

Describing compounds capable of more than one crystal structure

Front 30

simple cubic (SC)

Back 30

A crystal with cubic symmetry in which the atoms or ions are located at all eight corner positions.

Front 31

tetrahedral site

Back 31

A position in a crystal defined by four nearest neighbors

Front 32

unit cell

Back 32

The smallest representation of a material. In crystals the unit cell is the smallest patterned collection of atoms or ions that repeats in space

Front 33

volumetric density

Back 33

The number of atoms centered in a unit volume of crystal. Often the volume considered is the unit cell.