View
217
Download
0
Category
Preview:
Citation preview
8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)
1/7
Crystal
Microscopically,
a single crystal has atoms in a near-perfect periodic
arrangement; a polycrystal is composed of many microscopic crystals
(called "crystallites" or "grains");
an amorphous solid (such as glass) has no periodic
arrangement even microscopically.
A crystal or crystalline solid is a solid material whose
constituent atoms, molecules, or ions are arranged in anordered pattern extending in all three spatial dimensions.
large crystals are usually identifiale y their
macroscopic geometrical shape, consisting of flat faces
with specific, characteristic orientations
!he scientific study of crystals and crystal formation is
nown as crystallography.
!he process of crystal formation via mechanisms of crystal
growth is called crystalli#ation or solidification.
!he word crystal is derived from the Ancient $ree word
(krustallos), meaning oth %ice& and %roc crystal&
Unit cell
http://en.wikipedia.org/wiki/Single_crystalhttp://en.wikipedia.org/wiki/Periodic_functionhttp://en.wikipedia.org/wiki/Polycrystalhttp://en.wikipedia.org/wiki/Crystallitehttp://en.wikipedia.org/wiki/Amorphoushttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Order_and_disorder_(physics)http://en.wikipedia.org/wiki/Spatial_dimensionshttp://en.wikipedia.org/wiki/Crystallographyhttp://en.wikipedia.org/wiki/Crystal_growthhttp://en.wikipedia.org/wiki/Crystal_growthhttp://en.wikipedia.org/wiki/Crystallizationhttp://en.wikipedia.org/wiki/Solidificationhttp://en.wikipedia.org/wiki/Ancient_Greekhttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Quartz#Varieties_.28according_to_color.29http://en.wikipedia.org/wiki/Periodic_functionhttp://en.wikipedia.org/wiki/Polycrystalhttp://en.wikipedia.org/wiki/Crystallitehttp://en.wikipedia.org/wiki/Amorphoushttp://en.wikipedia.org/wiki/Glasshttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Atomhttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Order_and_disorder_(physics)http://en.wikipedia.org/wiki/Spatial_dimensionshttp://en.wikipedia.org/wiki/Crystallographyhttp://en.wikipedia.org/wiki/Crystal_growthhttp://en.wikipedia.org/wiki/Crystal_growthhttp://en.wikipedia.org/wiki/Crystallizationhttp://en.wikipedia.org/wiki/Solidificationhttp://en.wikipedia.org/wiki/Ancient_Greekhttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Quartz#Varieties_.28according_to_color.29http://en.wikipedia.org/wiki/Single_crystal
8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)
2/7
!he unit cell is a small ox containing one or more atoms, a
spatial arrangement of atoms. !he unit cells staced in three-
dimensional space descrie the ul arrangement of atoms of
the crystal. !he crystal structure has a three-dimensionalshape.
!he unit cell is given y its lattice parameters, which are the
length of the cell edges and the angles etween them, while
the positions of the atoms inside the unit cell are descried y
the set of atomic positions ( xi , yi , z i) measured from a lattice
point.
•
'imple cuic ()
•
ody-centered cuic (*)
•
+ace-centered cuic (+)
http://en.wikipedia.org/wiki/Honeycomb_(geometry)http://en.wikipedia.org/wiki/Miller_indexhttp://en.wikipedia.org/wiki/Honeycomb_(geometry)http://en.wikipedia.org/wiki/Miller_index
8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)
3/7
ithin the unit cell is the asymmetric unit, smallest unit the
crystal can e divided into using the crystallographic
symmetry operations of the space group. !he asymmetric unit
is also what is generally solved when solving a structure of amolecule or protein y -ray crystallography.
Microscopic Crystal structure (microscopic)
Microscopic structure of a halite crystal. (urple is sodium
ion, green is chlorine ion.)
!here is cuic symmetry in the atoms arrangement.
olymorphism is the aility of a solid to exist in more than
one crystal form.
+or example, water ice is ordinarily found in the hexagonal
form *ce *h, ut can also exist as the cuic *ce *c, the
rhomohedral ice **, and many other forms. !he different
polymorphs are usually called different phases.
http://en.wikipedia.org/wiki/Space_grouphttp://en.wikipedia.org/wiki/X-ray_crystallographyhttp://en.wikipedia.org/wiki/Halitehttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Chlorinehttp://en.wikipedia.org/wiki/Cubic_crystal_systemhttp://en.wikipedia.org/wiki/Polymorphism_(materials_science)http://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Ice_Ihhttp://en.wikipedia.org/wiki/Ice_Ihhttp://en.wikipedia.org/wiki/Ice_Ichttp://en.wikipedia.org/wiki/Ice_Ichttp://en.wikipedia.org/wiki/Rhombohedralhttp://en.wikipedia.org/wiki/Ice_IIhttp://en.wikipedia.org/wiki/Phase_(matter)http://en.wikipedia.org/wiki/Space_grouphttp://en.wikipedia.org/wiki/X-ray_crystallographyhttp://en.wikipedia.org/wiki/Halitehttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Chlorinehttp://en.wikipedia.org/wiki/Cubic_crystal_systemhttp://en.wikipedia.org/wiki/Polymorphism_(materials_science)http://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Ice_Ihhttp://en.wikipedia.org/wiki/Ice_Ichttp://en.wikipedia.org/wiki/Rhombohedralhttp://en.wikipedia.org/wiki/Ice_IIhttp://en.wikipedia.org/wiki/Phase_(matter)
8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)
4/7
+or pure chemical elements, polymorphism is nown as
allotropy.
+or example, diamond and graphite are two crystalline forms
of caron, while amorphous caron is a noncrystalline form.
olymorphs, despite having the same atoms, may have wildlydifferent properties. +or example, diamond is among the
hardest sustances nown, while graphite is so soft that it is
used as a luricant.
Defects, impurities, and twinning
!wo types of crystallographic defects. !op right/ edge
dislocation. ottom right/ screw dislocation.
An ideal crystal has every atom in a perfect, exactly repeating
pattern. 0owever, in reality, most crystalline materials have a
variety of crystallographic defects, places where the crystals pattern is interrupted. !he types and structures of these defects
may have a profound effect on the properties of the materials.
A few examples of crystallographic defects include vacancy
defects (an empty space where an atom should fit), interstitial
defects (an extra atom s1uee#ed in where it does not fit), and
dislocations (see figure at right).
http://en.wikipedia.org/wiki/Allotropyhttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Amorphous_carbonhttp://en.wikipedia.org/wiki/Edge_dislocationhttp://en.wikipedia.org/wiki/Edge_dislocationhttp://en.wikipedia.org/wiki/Screw_dislocationhttp://en.wikipedia.org/wiki/Crystallographic_defecthttp://en.wikipedia.org/wiki/Vacancy_defecthttp://en.wikipedia.org/wiki/Vacancy_defecthttp://en.wikipedia.org/wiki/Interstitial_defecthttp://en.wikipedia.org/wiki/Interstitial_defecthttp://en.wikipedia.org/wiki/Dislocationhttp://en.wikipedia.org/wiki/Allotropyhttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Amorphous_carbonhttp://en.wikipedia.org/wiki/Edge_dislocationhttp://en.wikipedia.org/wiki/Edge_dislocationhttp://en.wikipedia.org/wiki/Screw_dislocationhttp://en.wikipedia.org/wiki/Crystallographic_defecthttp://en.wikipedia.org/wiki/Vacancy_defecthttp://en.wikipedia.org/wiki/Vacancy_defecthttp://en.wikipedia.org/wiki/Interstitial_defecthttp://en.wikipedia.org/wiki/Interstitial_defecthttp://en.wikipedia.org/wiki/Dislocation
8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)
5/7
2islocations are especially important in materials science,
ecause they help determine the mechanical strength of
materials.
Another common type of crystallographic defect is an
impurity, meaning that the "wrong" type of atom is present ina crystal.
a perfect crystal of diamond would only contain caron atoms, ut a real crystal might perhaps contain a few
oron atoms as well. !hese oron impurities change the
diamonds color to slightly lue.the only difference etween ruy and sapphire is the
type of impurities present in a corundum crystal.
Chemical bonds
3rystalline structures occur in all classes of materials, with all
types of chemical onds. Almost all metal exists in a
polycrystalline state; amorphous or single-crystal metals must
e produced synthetically, often with great difficulty.
*onically onded crystals can form upon solidification of
salts, either from a molten fluid or upon crystalli#ation from a
solution.
3ovalently onded crystals are also very common, notale
examples eing diamond, silica, and graphite.
olymer materials generally will form crystalline regions, ut
the lengths of the molecules usually prevent completecrystalli#ation.
http://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Impurityhttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Diamond_colorhttp://en.wikipedia.org/wiki/Rubyhttp://en.wikipedia.org/wiki/Sapphirehttp://en.wikipedia.org/wiki/Corundumhttp://en.wikipedia.org/wiki/Chemical_bondhttp://en.wikipedia.org/wiki/Metallic_bondhttp://en.wikipedia.org/wiki/Ionic_bondhttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Moltenhttp://en.wikipedia.org/wiki/Covalenthttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Polymerhttp://en.wikipedia.org/wiki/Materials_sciencehttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Strength_of_materialshttp://en.wikipedia.org/wiki/Impurityhttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Diamond_colorhttp://en.wikipedia.org/wiki/Rubyhttp://en.wikipedia.org/wiki/Sapphirehttp://en.wikipedia.org/wiki/Corundumhttp://en.wikipedia.org/wiki/Chemical_bondhttp://en.wikipedia.org/wiki/Metallic_bondhttp://en.wikipedia.org/wiki/Ionic_bondhttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Moltenhttp://en.wikipedia.org/wiki/Covalenthttp://en.wikipedia.org/wiki/Diamondhttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Polymer
8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)
6/7
ea van der aals forces can also play a role in a crystal
structure; for example, this type of onding loosely holds
together the hexagonal-patterned sheets in graphite.
Properties
Crystal ParticlesAttractive
forces
Melting
point
ther
properties
*onic
ositive
andnegative
ions
4lectrostaticattractions 0igh
0ard, rittle,
good electrical
conductor inmolten state
Molecular olarmolecules
5ondon force
and dipole-dipole
attraction
5ow
'oft, non-
conductor or
extremely poorconductor of
electricity inli1uid state
Molecular 6on-polarmolecules
5ondon force 5ow 'oft conductor
Amorphous solid
*n condensed matter physics, an amorphous (from the $ree
a, without, morphé, shape, form) or non!crystalline solid is a
solid that lacs the long-range order characteristic of a crystal.
http://en.wikipedia.org/wiki/Van_der_Waals_forcehttp://en.wikipedia.org/wiki/Hexagonalhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Ionic_crystalhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Electrostatic_attractionhttp://en.wikipedia.org/wiki/Electrostatic_attractionhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Molecular_crystalhttp://en.wikipedia.org/wiki/Chemical_polarityhttp://en.wikipedia.org/wiki/Chemical_polarityhttp://en.wikipedia.org/wiki/London_forcehttp://en.wikipedia.org/wiki/Dipole-dipole_attractionhttp://en.wikipedia.org/wiki/Dipole-dipole_attractionhttp://en.wikipedia.org/wiki/Dipole-dipole_attractionhttp://en.wikipedia.org/wiki/Non-conductorhttp://en.wikipedia.org/wiki/Non-conductorhttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Condensed_matter_physicshttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Long-range_orderhttp://en.wikipedia.org/wiki/Crystalhttp://en.wikipedia.org/wiki/Van_der_Waals_forcehttp://en.wikipedia.org/wiki/Hexagonalhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Melting_pointhttp://en.wikipedia.org/wiki/Ionic_crystalhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Electrostatic_attractionhttp://en.wikipedia.org/wiki/Electrostatic_attractionhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Molecular_crystalhttp://en.wikipedia.org/wiki/Chemical_polarityhttp://en.wikipedia.org/wiki/Chemical_polarityhttp://en.wikipedia.org/wiki/London_forcehttp://en.wikipedia.org/wiki/Dipole-dipole_attractionhttp://en.wikipedia.org/wiki/Dipole-dipole_attractionhttp://en.wikipedia.org/wiki/Dipole-dipole_attractionhttp://en.wikipedia.org/wiki/Non-conductorhttp://en.wikipedia.org/wiki/Non-conductorhttp://en.wikipedia.org/wiki/Liquidhttp://en.wikipedia.org/wiki/Condensed_matter_physicshttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Solidhttp://en.wikipedia.org/wiki/Long-range_orderhttp://en.wikipedia.org/wiki/Crystal
8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)
7/7
Amorphous metals have low strength
Recommended