Chapter 5 Liquids and solids

5-3 Properties of Solids

固體的種類

� Crystalline Solid（結晶

固體）

� 分子或原子以固定的排

列方式形成的固體

� Amorphous Solid（非

結晶晶體）

� 分子或原子以隨意的排

列方式形成的固體

SiO2不同型態的固體

結晶固體的種類

金屬固體（Metallic Solids）

Mg（鎂）Zn （鋅）Ti （鈦）

Al （鋁）Cu（銅）Au（金）Ag（銀）

Fe（鐵）W （鎢）Li （鋰）Na（鈉）

hcp ccp bcc

六方最密堆積(hcp)的基本型態

立方最密堆積(ccp, fcc)

hcp與ccp的比較

20.688bcc

（體心立方堆積）

40.7412ccp

（立方最密堆積）

20.7412hcp

（六方最密堆積）

# of Atoms

in a Unit Cell

Packing

Density

Coordination

Number

Coordination Number

ccp hcp

Unit Cell

� Unit Cell : The smallest

building block of a crystal,

consisting of atoms, ions, or

molecules, whose geometric

arrangement defines a

crystal's characteristic

symmetry and whose

repetition in space produces

a crystal lattice

unitcell?

Example

� For each of the 2D

arrays shown here draw

a unit cell that, when

repeated, generates the

entire two-dimensional

lattice.

Unit Cell of bcc, ccp and hcp

From “Filling in the Hexagonal Close-Packed (hcp) Unit Cell”

In Journal of Chemical Education

Number of Atoms in a Unit Cell

PrimitiveCubic

Unit CellPo 釙

Packing Density

� Packing density : the

fraction of the total

volume occupied by

spheres

� Please calculate the

packing density of ccpa

4r

Holes in ccp

Octahedral Hole Tetrahedral Hole

Examples

� In a ccp crystal structure

� How many octahedral holes are there surrounding a

atom?

� How many tetrahedral holes are there surrounding a

atom?

� How many octahedral holes are there in a unit cell?

� How many tetrahedral holes are there in a unit cell?

Types of Unit Cells

� Bravais Lattice為自然

界中Unit Cell 的可能型

態，有14種不同的型態

How to Determine the Type of Unit Cell

� 測量晶體密度

� X-ray繞射

From : http://www.bruker-axs.de/fileadmin/user_

upload/xrfintro/sec1_8.html

Example

� The density of Cu is 8.93 g/cm3 and its atomic

radius is 128 pm. Is the metal more likely to be

(a) ccp or (b) bcc

X-ray Diffraction

Bragg Equation

From http://www.bruker-axs.de/fileadmin/user_

upload/xrfintro/sec1_8.html

θλ sin2dn =

Example

� In an x-ray diffraction experiment on a single

crystal of NaCl, with the use of radiation from a

copper source (λ=154nm), constructive

interference was observed at θ=11.2°. What is

the minimum spacing between the layer

responsible for the diffraction?

Ionic Solids

NaCl ZnS

Radius ratio

erl

smaller

r

r

arg

ionlarger of radius

ionsmaller of radius =

ratio Radius

=ρ

� ρ < 0.4 : cations fill the

tetrahedral hole

� 0.4< ρ < 0.7 : smaller ions

fill the octahedral hole

� ρ > 0.7 : anions form the

primitive cubic cell and

cations fill the large cubic

hole at the center

ρ > 0.7

CsCl and CsI

Exception Case of Ionic Structure

NiAs

Molecular Solids

� 分子固體固化的主要動

力為分子間作用力，其

能量遠比金屬鍵或離子

鍵小很多。因此分子固

體的沸點低，如：

� H2O

� C12H22O11

� UDPE超高密度聚乙烯

Network Solids – C

Diamond Graphite

CVD Diamond

From http://www.stanford.edu/group/microheat/two.html

Network Solids – SiO2

Quartz玻璃玻璃玻璃玻璃

固體的特性

Insulator or SemiconductorHighestCovalent bondNetwork Solids

InsulatorLowIntermolecular

interactions

Molecular Solids

Brittle

Insulator

HighIonic bondsIonic Solids

Luster

Malleability

Ductility

Good electric conductor

HighMetalic bondMetal

（Highest Density）

Characteristic PropertiesMelting Point

Luster（金屬光澤）

Malleability（金屬延展性）

Alloys（合金）

Substitutional Alloy Interstitial Alloy

Thermotropic Liquid Crystal

From http://www.laynetworks.com/Molecular-Orientation-in-Liquid-Crystal-Phases.htm

LCD 螢幕的原理

“Chemistry: The Molecular Nature of Matter and Change”

by Silberberg, Mc Graw Hill, 2000

Lyotropic Liquid Crystal