Diffraction - Sideversjonshistorikk

Elisaari på 24. mai 2009 kl. 14:34

2009-05-24T14:34:11Z

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 14:34
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	===Diffraction analysis===		===Diffraction analysis===

			==Electron Diffraction==

	[[Kategori: Teknikker i tools]]		[[Kategori: Teknikker i tools]]

Elisaari: /* X-ray diffraction */

2009-05-24T14:24:12Z

X-ray diffraction

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 14:24
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	*Generation of X-rays: X-rays are generated by acceleration of electrons on a pure metal target in ultra-high vacuum. Så må jeg si jeg ikke helt skjønner hva som skjer: hvilke elektroner dytter vekk hvilke? ++		*Generation of X-rays: X-rays are generated by acceleration of electrons on a pure metal target in ultra-high vacuum. Så må jeg si jeg ikke helt skjønner hva som skjer: hvilke elektroner dytter vekk hvilke? ++
	*Characteristic radiation		*Characteristic radiation

			===Aberrations===
			Caused by:
			*Variations in X-ray wavelength (non-monochromatic)
			*Variations in the angle of the incident beam with respect to the crystal (the rays of the beams are not strictly parallel).
	===Powder diffraction===		===Powder diffraction===
	Polycrystalline samples. The individual grains (single crystals) are randomly orientated in all directions)		Polycrystalline samples. The individual grains (single crystals) are randomly orientated in all directions)

Elisaari: /* X-ray diffraction */

2009-05-24T14:10:38Z

X-ray diffraction

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 14:10
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	==X-ray diffraction==		==X-ray diffraction==
			===Set-up===
	The X-ray diffractometer is composed of: a X-ray generator, a diffractometer assembly (controls the alignment of the beam as well as the position and orientation of the specimen and the X-ray detector), a detector assembly, X-ray data collection and processing systems.		The X-ray diffractometer is composed of: a X-ray generator, a diffractometer assembly (controls the alignment of the beam as well as the position and orientation of the specimen and the X-ray detector), a detector assembly, X-ray data collection and processing systems.
	*Generation of X-rays: X-rays are generated by acceleration of electrons on a pure metal target in ultra-high vacuum. Så må jeg si jeg ikke helt skjønner hva som skjer: hvilke elektroner dytter vekk hvilke? ++		*Generation of X-rays: X-rays are generated by acceleration of electrons on a pure metal target in ultra-high vacuum. Så må jeg si jeg ikke helt skjønner hva som skjer: hvilke elektroner dytter vekk hvilke? ++

Elisaari: /* Reciprocal space */

2009-05-24T14:09:55Z

Reciprocal space

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 14:09
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	*The limiting sphere and the Ewald's sphere:		*The limiting sphere and the Ewald's sphere:

	The limiting sphere: The values of sin<math>\theta</math> will lie between -1 and 1 and therfore 1/d has to lie between 0 and <math>2/\lambda</math> for a diffraction pattern to be generated. (Bragg's law has to be fulfilled). A sphere of radius 2/<math>\lambda</math> is then drawn, where the diffraction crystal is located at the center of the sphere. This sphere, containing all the possible values of 1/d for a given <math>\lambda</math> is called the limiting sphere.		'''The limiting sphere:''' The values of sin<math>\theta</math> will lie between -1 and 1 and therfore 1/d has to lie between 0 and <math>2/\lambda</math> for a diffraction pattern to be generated. (Bragg's law has to be fulfilled). A sphere of radius 2/<math>\lambda</math> is then drawn, where the diffraction crystal is located at the center of the sphere. This sphere, containing all the possible values of 1/d for a given <math>\lambda</math> is called the limiting sphere.

	The Ewald's sphere: A smaller sphere of radius 1/<math>\lambda</math> (1/2 of the limiting sphere), that lies in the limiting spere, which is placed so that it just touches the limiting sphere and also the the position of the crystal (the center). This is the Ewals's sphere, or reflecting sphere.		'''The Ewald's sphere:''' A smaller sphere of radius 1/<math>\lambda</math> (1/2 of the limiting sphere), that lies in the limiting spere, which is placed so that it just touches the limiting sphere and also the the position of the crystal (the center). This is the Ewals's sphere, or reflecting sphere.
	*The reciprocal lattice		*The reciprocal lattice

Elisaari på 24. mai 2009 kl. 14:08

2009-05-24T14:08:38Z

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 14:08
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			==Short facts==

			*Elastic scattering (no energy loss).
			*The wavelength of the radiation should be comparable to the interatomic spacing of the material.

	==Background==		==Background==
	Crystalline, polycrystalline and amorphous materials.		Crystalline, polycrystalline and amorphous materials.
Linje 4:		Linje 9:
	The crystal lattice: unit cell and point lattices. The seven crystal systems. Space groups. Miller indices and Unit vectors. Reciprocal space.		The crystal lattice: unit cell and point lattices. The seven crystal systems. Space groups. Miller indices and Unit vectors. Reciprocal space.

	=~~=Short facts==~~		===Bragg's law===

	*Elastic scattering (no energy loss).
	*The wavelength of the radiation should be comparable to the interatomic spacing of the material.

	==Bragg's law==
	*Condition: The planes of atoms responsible for a diffraction peak have to behave as a specula mirror, so that the angle of incidence <math>\theta</math> equals the angle of reflection.		*Condition: The planes of atoms responsible for a diffraction peak have to behave as a specula mirror, so that the angle of incidence <math>\theta</math> equals the angle of reflection.
	*Bragg's law		*Bragg's law
Linje 20:		Linje 20:
	In the BCC (body-centeres cubic) lattice the sum of h+k+l must be odd for an allowed reflection.		In the BCC (body-centeres cubic) lattice the sum of h+k+l must be odd for an allowed reflection.

	==Reciprocal space==		===Reciprocal space===
	Bragg's law imposes that the angles of diffraction are inversely proportional to the spacing of the lattice planes. It is therefore helpful to introduce a coordinate system where the axes have the dimensions of inverse length (nm^-1). This system of coordinates is referred to as the reciprocal space.		Bragg's law imposes that the angles of diffraction are inversely proportional to the spacing of the lattice planes. It is therefore helpful to introduce a coordinate system where the axes have the dimensions of inverse length (nm^-1). This system of coordinates is referred to as the reciprocal space.
	*The limiting sphere and the Ewald's sphere:		*The limiting sphere and the Ewald's sphere:

Elisaari: /* X-ray diffraction */

2009-05-24T14:07:37Z

X-ray diffraction

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 14:07
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	*Generation of X-rays: X-rays are generated by acceleration of electrons on a pure metal target in ultra-high vacuum. Så må jeg si jeg ikke helt skjønner hva som skjer: hvilke elektroner dytter vekk hvilke? ++		*Generation of X-rays: X-rays are generated by acceleration of electrons on a pure metal target in ultra-high vacuum. Så må jeg si jeg ikke helt skjønner hva som skjer: hvilke elektroner dytter vekk hvilke? ++
	*Characteristic radiation		*Characteristic radiation
	*Powder diffraction: Polycrystalline samples. The individual grains (single crystals) are randomly orientated in all directions)		===Powder diffraction===
			Polycrystalline samples. The individual grains (single crystals) are randomly orientated in all directions)

			===Single crystal diffraction===

			===Diffraction analysis===
	[[Kategori: Teknikker i tools]]		[[Kategori: Teknikker i tools]]

Elisaari: /* Reciprocal space */

2009-05-24T13:57:03Z

Reciprocal space

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 13:57
Linje 23:		Linje 23:
	Bragg's law imposes that the angles of diffraction are inversely proportional to the spacing of the lattice planes. It is therefore helpful to introduce a coordinate system where the axes have the dimensions of inverse length (nm^-1). This system of coordinates is referred to as the reciprocal space.		Bragg's law imposes that the angles of diffraction are inversely proportional to the spacing of the lattice planes. It is therefore helpful to introduce a coordinate system where the axes have the dimensions of inverse length (nm^-1). This system of coordinates is referred to as the reciprocal space.
	*The limiting sphere and the Ewald's sphere:		*The limiting sphere and the Ewald's sphere:
	The values of sin<math>\theta</math> will lie between -1 and 1 and therfore 1/d has to lie between 0 and <math>2/\lambda</math> for a diffraction pattern to be generated. (Bragg's law has to be fulfilled). A sphere of radius 2/<math>\lambda</math> is then drawn, where the diffraction crystal is located at the center of the sphere. This sphere, containing all the possible values of 1/d for a given <math>\lambda</math> is called the limiting sphere.
			The limiting sphere: The values of sin<math>\theta</math> will lie between -1 and 1 and therfore 1/d has to lie between 0 and <math>2/\lambda</math> for a diffraction pattern to be generated. (Bragg's law has to be fulfilled). A sphere of radius 2/<math>\lambda</math> is then drawn, where the diffraction crystal is located at the center of the sphere. This sphere, containing all the possible values of 1/d for a given <math>\lambda</math> is called the limiting sphere.

	The Ewald's sphere: A smaller sphere of radius 1/<math>\lambda</math> (1/2 of the limiting sphere), that lies in the limiting spere, which is placed so that it just touches the limiting sphere and also the the position of the crystal (the center). This is the Ewals's sphere, or reflecting sphere.		The Ewald's sphere: A smaller sphere of radius 1/<math>\lambda</math> (1/2 of the limiting sphere), that lies in the limiting spere, which is placed so that it just touches the limiting sphere and also the the position of the crystal (the center). This is the Ewals's sphere, or reflecting sphere.

Elisaari: /* Reciprocal space */

2009-05-24T13:56:35Z

Reciprocal space

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 13:56
Linje 25:		Linje 25:
	The values of sin<math>\theta</math> will lie between -1 and 1 and therfore 1/d has to lie between 0 and <math>2/\lambda</math> for a diffraction pattern to be generated. (Bragg's law has to be fulfilled). A sphere of radius 2/<math>\lambda</math> is then drawn, where the diffraction crystal is located at the center of the sphere. This sphere, containing all the possible values of 1/d for a given <math>\lambda</math> is called the limiting sphere.		The values of sin<math>\theta</math> will lie between -1 and 1 and therfore 1/d has to lie between 0 and <math>2/\lambda</math> for a diffraction pattern to be generated. (Bragg's law has to be fulfilled). A sphere of radius 2/<math>\lambda</math> is then drawn, where the diffraction crystal is located at the center of the sphere. This sphere, containing all the possible values of 1/d for a given <math>\lambda</math> is called the limiting sphere.

	The Ewald's sphere:		The Ewald's sphere: A smaller sphere of radius 1/<math>\lambda</math> (1/2 of the limiting sphere), that lies in the limiting spere, which is placed so that it just touches the limiting sphere and also the the position of the crystal (the center). This is the Ewals's sphere, or reflecting sphere.
	*The reciprocal lattice		*The reciprocal lattice

Elisaari på 24. mai 2009 kl. 13:49

2009-05-24T13:49:27Z

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 13:49
Linje 28:		Linje 28:
	*The reciprocal lattice		*The reciprocal lattice

			==X-ray diffraction==
			The X-ray diffractometer is composed of: a X-ray generator, a diffractometer assembly (controls the alignment of the beam as well as the position and orientation of the specimen and the X-ray detector), a detector assembly, X-ray data collection and processing systems.
			*Generation of X-rays: X-rays are generated by acceleration of electrons on a pure metal target in ultra-high vacuum. Så må jeg si jeg ikke helt skjønner hva som skjer: hvilke elektroner dytter vekk hvilke? ++
			*Characteristic radiation
			*Powder diffraction: Polycrystalline samples. The individual grains (single crystals) are randomly orientated in all directions)

	[[Kategori: Teknikker i tools]]		[[Kategori: Teknikker i tools]]

Elisaari: /* Bragg's law */

2009-05-24T12:04:03Z

Bragg's law

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 12:04
Linje 10:		Linje 10:

	==Bragg's law==		==Bragg's law==
	*Condition: The planes of atoms responsible for a diffraction peak have to behave as a specula mirror, so that the angle of incidence <math><\theta</math> equals the angle of reflection.		*Condition: The planes of atoms responsible for a diffraction peak have to behave as a specula mirror, so that the angle of incidence <math>\theta</math> equals the angle of reflection.
	*Bragg's law		*Bragg's law
	:<math> n\lambda=2dsin\theta </math>		:<math> n\lambda=2dsin\theta </math>