Chapter 2 Flashcards
is a crystal that contains no point, line, or planar defects
perfect crystal
are defects that occur only at or around a single lattice point
point defects
are lines along which whole rows of atoms in a solid are arranged anomalously
line defects
is discontinuity of the perfect crystal structure across a plane
planar defects
occur where the crystallographic direction of the lattice abruptly changes.
grain boundaries
occur in ordered alloys in this case the crystallographic direction remains the same, but each side of the boundary has an opposite phase
atiphase boundaries
occur in a number of crystal structures, but the common example is close-packed structures
stacking fruits
a defect that introduces a plane symmetry in the ordering of a crystal
twin boundary
a state where there is no pattern or arrangements
no order
arrangement of the atom extends only on the atom’s nearest neighbors
short-range order
each water molecule in steam has short-range order due to the covalent bonds
steam water
are joined together in a random manner. it may share corners, edgess, or faces
tetrahedral structure in silica
orderliness repeated over infinitely great distances.
long range order
have a crystalline structure in which the atoms or ions display long range order
MASCS
metals, alloys, semiconductors, ceramics, and some polymers
material forms a regular repetitive, grid-like pattern, in three dimensions
crystalline materials
the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries
single crystal
small crystallites with different crystal orientations that are separated by grain boundaries
polycrystalline materials
any material that exhibits only a short-range order of atoms or ions
amorphous materials
are formed due to kinetics of the fabrication of the material
amorphous material
a collection of lattice points, which are arranged in a periodic pattern
lattice
why lattice points are arranged in periodic pattern?
so that each point is identical
lattice can be how many dimensional
one, two, or three
a group of one or more atoms located in a particular way
basis
the smallest portion of a crystal lattice that shows the three dimensional pattern of the entire crystal
unit cell
three dimensional arrangements of lattice points
bravais lattices
a lattice named after auguste bravais who was an early french crystallographer
bravais lattices
Seven crystal systems
MHROCTT
monoclinic, hexagonal, rhombohedral, orthorhombic, cubic, triclinic, and tetragonal
directions within the unit cell in which the atoms are in continuos contact are
close packed direction
the number of atoms touching a given atom
coordination number
space occupied by atoms
packing factor
classifying solids based on bonds
MICM
metallic solids, ionic solids, covalent network solids, and molecular solids
are held together by a sea of collectively shared electrons
metallic solids
sets of cations and anions mutually attracted to one another
ionic solids
joined by an extensive network of covalent bonds
covalent network solids
descrete molecules held together by weak forces
molecular solids
long chains of atoms connected by covalent bonds, the chains are connected to other chains by weak forces
polymers
crystlline compounds with the crystals on the order of 1-100 nm
nanomaterials
solids with a regular repeating pattern of atoms is a
crystalline
lack of order in the arrangement of atoms
amorphous solids
basis of a repeating pattern is the unit cell
unit cell
the structure of the crystalline solid is defined by
a. the size and shape of the unit cell
b. the locations of atoms
geometric pattern on which the unit cell is based
crystal lattice
overall structure of the crystalline compound
lattice points
connects the points and define the unit cell
lattice vectors
have atoms only in the lattice points
primitive points
have atoms in another regular location
centered lattices
group of atoms that define the overall structure
motif
structures of many metals conform to one of the cubic unit
metallic structure
atoms in a crystal pack as close together as they can
close packing
three common types of packing
CHC
cubic close packed
hexagonal
close packed
