Pb La TiO : estudo por espalhamento Raman dos efeitos de ...
Espalhamento Raman
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Transcript of Espalhamento Raman
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Espalhamento Raman
Moléculas e sólidos
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Introdução
átomo
átomo
+ molécula
http://1.bp.blogspot.com/_iKSic4d4gPs/SXmKe_nueUI/AAAAAAAAAHE/YjseumSeyDk/s320/atom_pair.png
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Aproximando dois átomos
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Ligação molecular
http://employees.csbsju.edu/hjakubowski/classes/ch331/protstructure/ilennardjones2.gif
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Ligações moleculares: iônica
http://hyperphysics.phy-astr.gsu.edu/Hbase/chemical/bond.html#c4
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Lig. moleculares: covalente
http://hyperphysics.phy-astr.gsu.edu/Hbase/chemical/bond.html#c2
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Lig. moleculares: van der Waals
http://media-2.web.britannica.com/eb-media/71/22471-004-AA009DA2.gif
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Lig. moleculares: ponte de H
http://www.lbl.gov/images/MicroWorlds/H2OH-bond.gif
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Hydrogen-bonding-in-water-2D.png/800px-Hydrogen-bonding-in-water-2D.png
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Lig. moleculares: metálica
http://www.dorlingkindersley-uk.co.uk/static/clipart/uk/dk/sci_matter/image_sci_matter031.jpg
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Tipo de ligaçãopredomimante
van der Waals
Covalente
Iônica
Pontes de H
Metálica
Energia de ligação (eV)
0,01 (Ar) 0,1 (H2)
3,7 (Si)3,4 (InSb)
7,3 (KCl)
0,5 (gelo)
1,1 (Na)3,0 (Ag)4,4 (Ni)
Propriedades físicas típicas
Baixo ponto de fusão, isolantes elétricos, transparentes até UV
Rigidez e dureza, alto ponto de fusão, semi-isolantes
Isolantes elétricos em T baixa e condutores iônicos em T alta
Isolante elétrico, alta constante dielétrica, transparência VIS
Alta condutividade elétrica e térmica, opacidade, refletores de IR e transparentes ao UV
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Estados rotacionais
Momento angular é quantizado:
Energia do rotor rígido:
Consequentemente:
http://www.psnnewsletter.com/images/clients/330/n2_molecule_sm.gif
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Estados rotacionais
http://hyperphysics.phy-astr.gsu.edu/Hbase/molecule/rotrig.html#c1
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Estados vibracionais
Oscilador harmônico:
onde
e
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Estados vibracionais
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Cte. de força: Coulomb
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Constante de força
MoléculaFreqüência
x1013 HzConstante de força
N/m
HF 8.72 970
HCl 8.66 480
HBr 7.68 410
HI 6.69 320
CO 6.42 1860
NO 5.63 1530
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Tipos de vibração: CO2
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Vibração e rotação combinadas
Modos rotacionais e vibracionais são excitados simultaneamente:
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Vibração e rotação combinadas
Para a transição de estado l+1 para l, a energia do fóton é:
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Transições ópticas
http://hyperphysics.phy-astr.gsu.edu/HBASE/molecule/molec.html#c2
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Espectros de emissão típicos de moléculas
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Espectro de absorção HCl
http://hyperphysics.phy-astr.gsu.edu/Hbase/molecule/imgmol/hclspec2.gif
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Espalhamento Raman
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Combinação linear de orbitais atômicos
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Ligante e anti-ligante
http://hyperphysics.phy-astr.gsu.edu/HBASE/molecule/hmol.html#c1
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Ligante e anti-ligante
http://hyperphysics.phy-astr.gsu.edu/HBASE/molecule/hmol.html#c1
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Hibridização:sp, sp2, sp3
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Mínimo da energia total distância de equilíbrio
No caso de sólidos (at. iguais), energia mínima quando mesma vizinhança.
Arranjo 3D periódico
Estado cristalino
+ de 1 tipo de at. dist. periódicas de grupos definidos
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Redes de translação
a
b
a = b
90o a
b
90o
a
b
90o
a
b
a
b
= 60o
a = b
paralelogramoquadrada retangular
retangular centrada hexagonal
2D
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7 sistemas cristalinos em 3D
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14 Redes de Bravais
Espaço 3DGrupos espaciais
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“RB : conjunto periódico no qual as unidades repetidas do cristal estão dispostos”
unidades = átomos, moléculas, íons, etc.
2 definições equivalentes:
(a) Uma RB é um conjunto infinito de pontos discretos com um arranjo e orientação que parece exatamente o mesmo, visto a partir de quaisquer dos pontos do conjunto
(b) Uma RB (3D) consiste de todos os pontos do tipo:
vetores primitivosinteiros (pos. ou neg.)
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Estruturas cristalinas simples
Cúbica de face centrada (fcc)
Ex:Cu, Ag, Au, Ni, Pd, Pt, Al …
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Hexagonal compacto (hcp)
Ex:
Be, Cd, Ce, -Co, Dy, Er, Gd, Hf, Ho, La, Lu, Mg, Nd, Os, …
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Hexagonal compacto (hcp)
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Hexagonal compacto (hcp)
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Hexagonal compacto (hcp)
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Cúbica de corpo centrado (bcc)
Ex:
Metais alcalinos, Ba, V, Nb, Ta, W, Mo, …
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Diamante
Ex:C (diamante)SiGe-Sn
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Blenda de zinco (ZB)
Ex:CuF, CuCl, CuBr, CuI, AgI, BeS, BeSe, BeTe, MnS, MnSe, ZnS, ZnSe, ZnTe, CdS, CdTe, HgS, HgSe, HgTe, AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, InSb, SiC
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NaCl(fcc interpenetradas)
CsCl(sc interpenetradas)
Estruturas iônicas
Ex:CsCl, CsBr, CsI, TlCl, TlBr, TlI
Ex:LiF, LiCl, LiBr, LiI, NaF, NaCl, NaBr, NaI, KF, KCl, KBr, KI, …