X-ray diffraction is an wonderful technique. X-rays have wavelengths of the order of the atomic spacing. So atoms in crystal act like grating in optical diffraction where the spacing is much larger and so also is the wavelength of light. This idea came to the head of Max von Laue while walking in the Englischer Garten in Munich with Ewald who just finished writing a thesis on a similar but more abstract topic. The experiment was done at the Munich university and diffraction spots were discovered. This simultaneously proved wave nature of X-rays and also the periodic lattice formed by the atoms in crystals. Max von Laue received Nobel prize for this great work. Being a theoretical physicist he was not too much interested in the applied work of solving crystal structures of all the materials of the world. But Braggs (W.H and W.L.) were interested in this practical applications. They soon realized that X-ray diffraction pictures are nothing but the Fourier transform of the configuration of scattering centers, albeit the phases of the wave fronts were missing in the diffraction picture. X-rays unlike ordinary light cannot be focused. So we cannot make a picture of the scattering centers as the optical instruments (for example our eye) can do. So the missing phase was the hindrance for solving crystal structure. So Braggs had to go through model making and solve the structure by trial and error. Soon however clever techniques like Patterson synthesis were found. Eventually direct methods of finding phases and determining structures were also found.
You must remember that solving structures has two very important steps. (1) The first easy step (if you have single crystals) is to find the lattice periodicity and its symmetry and also guess the possible space groups. This can be done from the positions of the diffraction spots and systematic absences. (2) But the detailed positions of the atoms arranged in the lattice require require the intensity information of the Bragg spots. If the phases were also available then the structure determination would be a simple exercise of calculating Fourier inverse transform. But unfortunately they are missing and therefore intelligent methods described before (Patterson or direct methods) have to be used.
All the books I and my colleagues suggested you describe these two steps in more details.
You can find information in the literature looking up books such as "Solid State Physics" Ashcroft&Mermin or "Introduction to Solid State Physics" Kittel
Hi Jack, I think a very good reference about X-ray diffraction is the book "Elements of X-ray diffraction" by B.D. Cullity
for your sample you will get diffraction data 2theta and intensity, you can match it with JCPDS card and you can find which type of crystal is your sample
what type measurement you do? If you use rocking curve scan or also know as omega scan you can determine the quality by using its FWHM (full-width at half maximum) value. If you get a narrower peak it mean your sample has better quality.
This question is one hundred years old. Young W.L. Bragg asked this question to himself and then answered it and then soon received the Nobel prize jointly with his Dad! Jack Daniels I humbly request you to read a bit of the vast literature before you learn to use the all black box magic programs that helps to solve structures blindly without understanding.
The books suggested by my colleagues are all good introductory books. You can add to the list the book by B.E. Warren, "X-ray diffraction", which is one of the best book. If you wish to hear the story from the horse's mouth then please read the book by W.L. Bragg, "Development of X-ray analysis". Both the books are available in cheap Dover edition. For a modern introduction to the subject you can consult the book "Elements of Modern X-ray Physics", 2nd Edition, Jens Als-Nielsen, Des McMorrow.
However if you are thinking single-crystal X-ray structure determination rather than powder X-ray diffraction then I shall suggest you to read the very practical book, "X-ray structure determination" by Stout and Jensen and also a more theoretically oriented "X-ray crystallography" by M.M. Woolfson.
X-ray diffraction is an wonderful technique. X-rays have wavelengths of the order of the atomic spacing. So atoms in crystal act like grating in optical diffraction where the spacing is much larger and so also is the wavelength of light. This idea came to the head of Max von Laue while walking in the Englischer Garten in Munich with Ewald who just finished writing a thesis on a similar but more abstract topic. The experiment was done at the Munich university and diffraction spots were discovered. This simultaneously proved wave nature of X-rays and also the periodic lattice formed by the atoms in crystals. Max von Laue received Nobel prize for this great work. Being a theoretical physicist he was not too much interested in the applied work of solving crystal structures of all the materials of the world. But Braggs (W.H and W.L.) were interested in this practical applications. They soon realized that X-ray diffraction pictures are nothing but the Fourier transform of the configuration of scattering centers, albeit the phases of the wave fronts were missing in the diffraction picture. X-rays unlike ordinary light cannot be focused. So we cannot make a picture of the scattering centers as the optical instruments (for example our eye) can do. So the missing phase was the hindrance for solving crystal structure. So Braggs had to go through model making and solve the structure by trial and error. Soon however clever techniques like Patterson synthesis were found. Eventually direct methods of finding phases and determining structures were also found.
You must remember that solving structures has two very important steps. (1) The first easy step (if you have single crystals) is to find the lattice periodicity and its symmetry and also guess the possible space groups. This can be done from the positions of the diffraction spots and systematic absences. (2) But the detailed positions of the atoms arranged in the lattice require require the intensity information of the Bragg spots. If the phases were also available then the structure determination would be a simple exercise of calculating Fourier inverse transform. But unfortunately they are missing and therefore intelligent methods described before (Patterson or direct methods) have to be used.
All the books I and my colleagues suggested you describe these two steps in more details.
To add furhter historic information on the Laue's and coworkers achivements. Laue discussed (what Tapan said in his last comment) with colleagues Sommerfeld and Wien and others, with the result of encountering a strong disbelief of finding any diffraction experimental based upon the regularity of the internal structure of crystals. Sommerfeld claimed that the inevitable temperature motion of atoms would impair the regularity of the gratiing to such way that no pronounced diffraction could be expected. In fact Sommerfeld thought that a diffraction grating whose vibrations are the same size as the incoming waves hardly seemed to pose a promising experiment, and Sommerfeld was reluctant to devote financial support on this enterprise (It took some years to understand why the thermal agitation can not wipe out the x-ray interference). Friedrich, Knipping and Laue with equipment pirated were able to get successful diffraction spots after different attempts. This achievement is one of the most important ones in Condensed Matter Physics and teach us that giving full freedom to scientist to pursue directions or routes that emanate from their curiosity and scientific imagination, cutting-research allows to get insight and explore new terrain with unintended consequences, as Bragg's family and following researchers also showed .
Reading from google
You have the intensity peaks and the diffraction angles. Let's say you suspect the material is cubic, how do I find if it's simple cubic or BCC or FCC?
You are measuring the k-space (reciprocal lattice space) points with the x-ray diffraction. The Fourier transform of these points (provided you measured enough of them) gives you exactly the Bravais lattice.
The Bravais lattice is the crystal stucture! You then have to look at the Bravais lattice and construct a Wigner-Seitz unit cell, then that construction will determine your crystal type
The overenthusiatic crystallographers who now captured the field meanwhile started writing suitable programs to make the life easy for people that were interested to solve the crystal structures by the X-ray diffraction technique. The development of powerful computers helped them enormously. So after a century X-ray diffraction technique has now become unfortunately almost a black box routine method. One feeds the intensity data to the computer and out come the structural parameters. At least that's what the younger generation wishes. They make hardly any effort to understand the basic principles. This is a real pity!!
You must also note the fantastic development of the diffraction technique in general during the last few decades. Synchrotron X-rays became available. One can now tune the X-ray wavelength close to the absorption edge and study several intricate and complex phenomenon. You can even look at details of magnetic structure, orbital ordering. Complex phenomenon like charge ordering can also be investigated by synchrotron X-ray diffraction. But you should also not forget the similar neutron diffraction and electron diffraction and microscopy. Neutron diffraction and scattering became the major microscopic tool for investigating magnetic materials. Electron diffraction can now be used to solve the structures despite the complication due to strong dynamical scattering effects in this method. Fantastic advantage of electron diffraction is that in fact we can do microscopy because electron beam can be focussed. So unlike X-ray diffraction we can produce direct pictures of atoms or groups of atoms. The nanoscience would not be possible without the electron microscopy. So you see although solving just the crystal structures by X-ray diffraction has now become a routine technique there are enough new exciting fields, which have evolved in condensed matter physics where the scattering methods still contribute very much and are extremely useful. To participate in all these new developments the condensed matter scientist must understand the basic principles of scattering method and should not be just dependent on back-box magic programs.They should be able to think and even develop new methods in this field. Soon we will have X-ray lasers and coherent beams and you can guess what scattering techniques can achieve with these new developments!!
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"También debe tener en cuenta el fantástico desarrollo de la técnica de difracción, en general, durante las últimas décadas. Los rayos X de sincrotrón se hizo disponible. Ahora uno puede sintonizar la longitud de onda de rayos X cerca del borde de absorción y estudiar varios fenómeno intrincado y complejo. Usted puede incluso ver los detalles de la estructura magnética, pedidos orbital. Fenómeno complejo como el ordenamiento de carga también puede ser investigado por sincrotrón de difracción de rayos-X. Pero también no hay que olvidar lo similar difracción de neutrones y difracción de electrones y microscopía. Difracción de neutrones y microscópica de dispersión se convirtió en la principal herramienta para la investigación de los materiales magnéticos. Difracción de electrones se puede utilizar ahora para resolver la complicación estructuras debido a la fuerte a pesar de los efectos de dispersión dinámicos en este método. Fantástico ventaja de difracción de microscopía electrónica es que, de hecho, que podemos hacer ya que el haz de electrones puede ser enfocado. Así que a diferencia de difracción de rayos X podemos producir imágenes directas de átomos o grupos de átomos. La Nanociencia no sería posible sin la microscopía electrónica. Así que ya ves, aunque la resolución sólo las estructuras cristalinas por difracción de rayos X se ha convertido en una técnica de rutina hay suficientes nuevos campos emocionantes, que han evolucionado en la física de la materia condensada, donde los métodos y estilo de dispersión contribuyen a mucho y son de gran utilidad. Para participar en todas estas novedades el científico de la Materia Condensada debe entender los principios básicos de los métodos de dispersión y no debe ser sólo depende de back-cuadro programs.They magia debe ser capaz de pensar e incluso el desarrollo de nuevos métodos en este campo. Pronto tendremos vigas y láseres de rayos X y técnicas de dispersión coherente puede adivinar lo que puede lograr con thes nuevos desarrollos !!"
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Dear A. Ouerdane
I want to use this method for one phase (with unknown crystal structure, but known composition by EPMA). My sample has three phases (under SEM). Two of them have known XRD Pattern (JCPDS reference). From the XRD pattern of this sample I want to determine the unknown crystal structure of the third phase..
Being a beginner I would like to kindly request you a more detail explanation (or any reference) about what procedure i have to follow? By the way, I am using X'Pert HighScore Plus (V. 3) program for Rietveld refinement.
I need help with the same too :,( ...
recommend me some books, software or something to could obtain the structure from XDR ...please
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