Crystalline Solids

Crystalline solids have ____ ordering.

periodic

Amorphous solids lack ____.

periodic ordering

which is the crystalline solid and which is the amorphous solid

a unit cell is ____ in all directions

repeated

what are the seven crystal systems?

cubic, tetragonal, orthorhombic, monoclinic, triclinic, trigonal, hexagonal

Seven crystal systems flow chart

For cubic solids, what are the allowed symmetries, what are the unit cell shapes?

primitive, body-centered, face-centered

For tetragonal solids, what are the allowed symmetries, what are the unit cell shapes?

primitive, body-centered

what symmetry does this structure have?

face-centered, atoms occupy center of each face of the structure

what symmetry does this structure have?

body-centered, atoms on corners and atom directly in center

what symmetry does this structure have?

primitive, only atoms on corners

To be body-centered, all atoms MUST _____ on the structure.

be the same

cubic symmetry cannot have ____ symmetry

end-centered

For Trigonal (rhombohedral) solids, what are the allowed symmetries, what are the unit cell shapes?

can only have primitive,

For orthorhombic solids, what are the allowed symmetries, what are the unit cell shapes

primitive, body-centered, face-centered, end-centered

What type of symmetry does this solid have

end-centered, atoms on corners and one in center of two faces

For monoclinic solids, what are the allowed symmetries, what are the unit cell shapes

primitive and End-centered

every structure can have a ____ structure

triclinic

what is the lowest symmetry crystal system?

triclinic

Cubic: Four __ axes, three __ axes

3, 4

tetragonal: one __ axis

4

to go from cubic to tetragonal:

stretch/compress along one axis

to go from tetragonal to orthorhombic:

stretch/compress along second axis

to go from orthorhombic to monoclinic:

shear one face relative to opposite facet

o go from monoclinic to triclinic:

shear a second face relative to opposite face

Orthorhombic: three __ axes or ____

2, mirror planes

Monoclinic: one __ axis or __

2, mirror plane

Monoclinic: one __ axis or __

2, mirror plane

Triclinic: no __ or ____ symmetry

axial, mirror

To go from cubic to trigonal:

stretch/ compress along one body diagonal

trigonal: one __ axis

3

triclinic solids have what symmetry, what are the unit cell shapes

primitive

corner site, face site, edge site

how much do the corner atoms, edge atoms, and face atoms account for?

corners: 1/8

edges: ¼
faces: ½

what is the chemical formula for this salt structure?

____ of spheres is most efficient and most common in nature.

close-packing

Cubic Face Centered packing sequence:

ABCABC

Hexagonal packing sequence:

ABABAB

interstitial holes:

hexagonal and cubic close-packing

interstitial holes form ____ and ___ shaped holes

octahedral and tetrahedral

fluorite chemical structure

MX₂

antifluorite chemical structure

M₂X

anti fluorite structure reverses position of

metal and fluorine

Zinc blends have a cation:anion ratio of?

1:1

CN for Ti = 6 , CN for O = 3

If Ti occupies the center of a cubic unit cell and Ba occupies the corners and O each face, what is the empirical formula of the compound?

General formula for perovskites:

ABO3

What is lattice energy

How much energy it takes to form/break down into gaseous ions

most useful properties of solids are related to:

___ vibrations of atoms or ions

the presence of _____

the existence of ____

thermal vibrations, impurities, defects

Examples of defects:

simple ____

unexpected occupation of ____ sites

incorporation of ____: atoms or ions

Various ____ imperfections

vacancies, interstitial sites, impurities, lattice

Schottky Defect:

the difference in size between cation and anion is ___.

Both anion and cation ___ the solid crystal.

Atoms ____ leave the crystal.

There is formation of two ____.

The density of the solid ____.

small, leave, permanently, vacancies, decreases

Frenkel Defect:

Contains ionic crystals where the ___ is larger than the ____.

Usually the ___ ion cation leaves its original lattice structure.

Atoms ___ within the solid crystal.

only ___ vacancy is created.

____ remains the same.

anion, cation

smaller, one, density

In solids, atomic orbitals overlap —> energy levels spread into ___

bands

Valence band

usually filled with electrons

conduction band

higher energy states, may be empty or partially filled

Band gap:

energy separation between valence and conduction bands

a charge carrier in a semiconductor, is either a _____ or an electron that is able to ___ electricity.

positive hole, conduct

The valence bands participate in ___ and ____

bonding, magnetism

The ___ band is the empty ____

conduction, LUMO

Which is the conduction band, which is the valence band

label the three conductors

This is an ____

band gap is so big, energy jump is unable to be made

fermi level is the ?

measure of the energy of the least tightly held electrons within a solid

The electrical conductivity of a ____ decreases with temperature; that of a ______ increases with temperature.

metal, semiconductor

this graph is for ___ and ____

metals and semi conductors

this graph is for ____

insulators

a dopant is an ____ introduced into a semiconductor in minute amounts to enhance its _____.

impurity electrical conductivity

____ contain dopants

extrinsic semiconductors

p-type semiconductor:

Group ____ element is added as a doping element

Trivalent impurity like __, __, __, etc. are added, NOT B

The fermi level is between acceptor energy level and the valence band, closer to the ____ band than the ____ band.

III

Al, Ga, In

valance, conduction

N-type semiconductor:

Group __ element is added as a doping element

Pentavalent impurity like __ , __, __, __etc. are added NOT N

Fermi Level is between donor energy level and the conduction band, appears closer to the ___ band than the ___ band

V

P, As, Sb, Bi

conduction, valence

what are these types of conductors?

The semiconductor on the left is a p-type semiconductor, the fermi level is closer to the valence band than the conduction band

The semiconductor on the right is an n-type semiconductor, the fermi level is closer to the conduction band than the valence band