5-3 properties of solids
TRANSCRIPT
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