2 wiki phys crystal & amorph fafi (1)

8/18/2019 2 Wiki Phys Crystal & Amorph Fafi (1)

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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


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!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


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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)


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+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


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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


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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


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Amorphous metals have low strength

2 wiki phys crystal & amorph fafi (1)

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