Questions tagged [x-ray-crystallography]

X-ray crystallography encompasses the structural characterization of crystalline materials by means of X-rays. This is done most commonly by X-ray diffraction, which can be applied to monocrystalline materials or heterostructures, as well as to polycrystalline materials, where the later is referred to as powder X-ray diffraction.

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Is the Compton effect observed during regular x-ray diffraction?

Here we have the standard set up to observe the compton effect. From what I understand, due to the particle like nature of light, when the x ray photons collide with the electrons in the scatterer ...
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Can faster sampling frequency solve the x-ray diffraction phase problem?

In the x-ray diffraction, only the intensity the light that hits the detector is captured while the phase of the light is not determined. The energy flux of the light is the Poynting vector. For a ...
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Extinction Rules In cubic lattices FCC and BCC

I was recently looking at structure factor of different cubic lattices BCC and FCC and came across something called the extinction rule which I am having a hard time visualizing. So and example is ...
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Intensity of x-ray difracted on a crystal

Suppose we have an X-ray tube R which emits X-rays of intensity $I_s(\lambda)$, obeying the Kramers' law. The X-rays then come to the cubic crystal K under the angle $\vartheta$, where diffraction ...
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Geiger Counter vs PIN Detector

I have noticed in many papers that test Moseley's law use PIN detectors instead of Geiger counters to measure the XRF spectrums of elements. Why is that? is it because Geiger counters signal also ...
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Dependence on sample thickness and incident intensity in X-ray crystallography?

In X-ray crystallography, a sample (let's say a crystal or a quasicrystal) is illuminated with X-rays. These scatter from it and form an interference pattern, which will be composed of Bragg peaks, ...
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Why are experimental atomic scale images black and white?

XRay diffraction patterns are black and white. So are scanning electron microscope (SEM) images. Why is this so? At the time of measurement at the atomic level, do the atoms fail to absorb or emit ...
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Scattering on crystals beyond Ewald and Bragg

So I whenever we consider the diffraction and scatting using crystals, powders, basically anything crystalline in the lab using X-rays we get a bunch of theories and models. The most simple one would ...
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Elastic X-ray diffraction: Where does the Photon Momentum go to?

lately I was discussing the following situation. Let's suppose you are doing X-Ray diffraction experiments on a crystal. So what you basically do is shooting a high energy photon with a wave vector $k$...
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Positron beams and crystallography

I wad mainly reading about impact and uses of positron beam to determine conductivity and the structure of material . Do can anyone just describe how positron beams can determine conductive of ...
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Origin of XRD Peak Asymmetry

I have been doing an introductory XRD experiment in which we measure the crystal spacing of a simple lattice (LiF) and as usual obtained data for intensity against two theta. Ideally the peaks should ...
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Can we call a hexagonal system with two different atoms as inversion symmetric?

Graphene is two-dimensional honeycomb crystal lattice with the two Carbon atoms in its unit cell. Clearly, it is inversion symmetric. But, suppose we have two different atoms in the hexagonal system ...
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Why is intensity decreasing for higher orders of Bragg (x-ray)diffraction?

Bragg diffraction for x-rays by a crystal structure is governed by $$ n\lambda=2dsin\theta ,$$ where $n$ is an integer and the diffraction order, $\lambda$ is the x-ray wavelength, $d$ the lattice ...
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X-ray frequency or crystal structure: which was known first?

In the classical Bragg setup, one can determine the distance between crystal layers if the wavelength of a characteristic line is known or the other way round, calculate the distance if the wavelength ...
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Structure Factor for diffraction patterns

im trying to figure out myself the use of Structure Factor for Diffraction patterns. I have the Structure Factor for a monoatomic lattice $S(\overline G)=\sum_{i=1}^n f e^{\overline G \cdot \...
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Comparison between X-ray diffraction and slit experiment

Most diagrams regarding X-ray diffraction suggest that after hitting an atom, X-ray would get reflected. But then the method results in an interference pattern which means X-ray get diffracted. I am ...
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Using Miller indices to determine interference from a particular plane in a crystal lattice

In terms of x-ray diffraction from crystals. I was wondering how you can use the miller indices to determine whether there will be constructive or destructive interference from a particular plane in ...
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How can I tell the cubic structure of different crystals?

So I have a couple of crystals I am analysing (LiF RbCl NaCl...) and I have the x ray diffraction patterns for them. How do I determine the different structures of these crystals as I need to ...
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Why the first peak in the X-ray diffraction of an amorphous solid has significantly high, in terms of intensity than the second peak?

In the XRD pattern of an amorphous solid we do not observe sharp peaks. Instead we see only diffused peaks. Why these peaks are diffused and more importantly why the first peak is significantly high ...
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Why is base centered lattice not possible in cubic system?

It still has symmetry,then why is the existence of base centered lattice not possible? Is it that it is impossible or is it that we have seen none like that in real?
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Issues with Miller indices

I have read that to find the intercepts of a plane represented by Miller indices is to take the reciprocal of each index. However, I noticed that does not give the original plane if we had to reduce ...
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Phase Retrieval and Oversampling

In signal and image processing theory, it is known that taking the Fourier transform of a zero-padded image gives the oversampled Fourier transform of the image. And that oversampling is a necessary ...
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What causes Lorentzian broadening of X-ray diffraction peaks?

In X-ray diffraction, the pseudo-Voigt model is a combination of Gaussian and Lorentzian distributions, and is often used to model peaks. The form of the peak is often described as $V(x)$ = (1-$\...
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Why/when can the chemical structure of crystals be assumed to be diffraction gratings?

Why/when can the chemical structure of crystals be assumed to be diffraction gratings? Like how does one know a priori, whether the structure is like a diffraction grating, if one doesn't yet know ...
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How to determine the degree of how high a symmetry of high-symmetry points in the first Brillouin zone?

For exmple, we have a hexagonal lattice with hexagonal Brillouin zone, shown in the picture The points $\Gamma$, K, M and $\Lambda$ are high symmetry points. Now, $\Gamma$ point is the highest-...
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Meaning of crystal orientation

If I have a crystal, say (001)-oriented ABO3, what does the 001 imply, from an experimental perspective? I understand that the 001 is referring to a plane as described by Miller indices, but what is ...
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Miller indices and FCC structure - non-existent planes

Below is a copy from Kittel's Introduction to Solid State Physics, 8th edition, page 42. It is a picture to illustrate that in FCC structures (loosely said and exactly cited) "no reflections can ...
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SAXS: Why would a second order peak behave differently than first order?

What is the significance of a second order peak in SAXS and during an assembly of nanoparticles, why would it have a different shape over time: What are factors that are unique to first or second ...
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How to calculate the lattice constant of NaCl using chemical information? [closed]

More specifically, how would I show that: $a_0=\sqrt[3]{\frac{4M}{N_A\rho}}$ where $a_0$ is the lattice constant, M is the molecular mass of NaCl, $\rho$ is the density of NaCl, and $N_A$ is ...
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Why is $K_{\alpha,3/2}$ always more intense than $K_{\alpha,1/2}$ in copper?

Consider characteristic X-ray emission from copper. The $K_{\alpha}$ line is a doublet because of the spin-orbit interaction. But why is the $K_{\alpha,3/2}$ line always more intense than the $K_{\...
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174 views

Debye-Waller factor from X-ray diffraction data

I'm conducting a X-ray diffraction experiment for lab, but am new to solid-state physics and crystallography. I have to find the Debye-Waller factor (DWF) of Al at room temperature using X-ray powder ...
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195 views

Structure factor calculation for non-cubic lattices

I have an equilibrated trajectory from a molecular dynamics simulation and I would like to calculate the structure factor using the atomic positions. I think I am able to do it right for cubic ...
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Why do we do a linear regression to find the minimum wavelength in a X-Ray diffraction spectrum?

As part of a an experiment, I was to determine the minimum wavelength emitted by an x-ray source through analysing the detected count rate (detected by a GM counter) of a diffracted x-ray source, via ...
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How to find which crystal planes are symmetric

Is there a strict mathematical procedure to find all equivalent planes given a unit cell and a particular plane of interest? For example, consider a conventional FCC unit cell and the (100) plane. I ...
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Relative intensity in powder method

I cracked KCl and made two samples. One is a fine powder, another is a coarse powder. Using these samples, diffraction intensity was measured. The results were as followed. ...
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How to find the Miller indices for a family of planes

So I'm a bit confused about this question This question asks for the miller indices for the "families of planes". Is there a single set of Miller indices for each cubic unit cell which I can use to ...
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How do we find the angle of incidence $\theta$ in a Bragg diffraction experiment?

Suppose I have a crystal of which I like to determine the distance $d$ between the lattice planes. We can use a Bragg diffraction experiment to do so by making a plane wave of X-ray radiation with ...
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Medical X-Ray - why no diffraction?

When I go to a doctor and he wants to see my bones he uses X-Ray. My bones contain crystalline material called hydroxyapatite. Why the result of imaging is the shape of my skeleton and not just XRD ...
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Is there a known physical crystal for each space group? [duplicate]

Group theory tells us that there are 230 crystallographic spaces possible in 3D space. Is there physically at least one crystal known to form every in each space group, or are certain space groups ...
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Does X-Ray Diffractometry actually involve diffraction?

To my understanding, diffraction is the bending of waves as they pass by edges or go through slits. However, I cannot find a description of x-ray diffractometry that actually involves diffraction. All ...
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Why use simple cubic reciprocal lattice vector to determine Miller indices?

Bragg diffraction: $$ d_{hkl}= \frac{\lambda}{2sin(\theta)}.$$ This equation would allow us to determine the lattice spacing ($d_{hkl}$) of parallel crystal planes given that we observe an intensity ...
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XRD with random orientation

How can XRD examine a randomly oriented crystal lattice. Doesn't it needs a tidy structure? Why does the diffractogram always show the same image even when we change the sample(the sample shoulder ...
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How can a monochromatic X-Ray tube produce a spectrum in XPS?

I thought that if we use monochromatic source, we can only get one peak, if it exists. Because Photoelectric Effect allows only the electron that have the corresponding frequency(energy level) that ...
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How do I determine the $n$ integer in the Bragg's law?

I'm studying X-rays crystallography. The basic assumption is that if I let some X-rays scatter on a crystal the atoms act as sources of new waves. Considering two waves that hit two "neighbouring" ...
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X-Ray Diffraction: Why does FCC have MORE peaks than SC?

Reading Kittel, I understand that the structure factor of an fcc lattice is such that there is only scattering from those planes with all even or all odd indices. He then shows XRD for KCl and KBr ...
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Crystallite size in thin films

First thing is, what is the difference between grain size and crystallite size? Well, I have basic knowledge between the two. As far as I know the grain size is single crystal within the bulk/thin ...
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Why is amplitude of x-rays scattered by crystal is less than the amplitude of rays incident on crystal? [closed]

Why is amplitude of scattered rays less than the amplitude of rays incident on crystal? Also what will be the situation in case of free electrons?
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How to go from space group to crystal structure?

I'd like to easily be able to define a group of lattice points for any crystal structure, with or without a basis. It seems the space group is the most commonly given quantity describing the ...
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Why aren't there Bragg peaks from sublattices of the unit cell?

I've been struggling with what is probably a basic question about Bragg peaks, diffraction, and I guess geometric structure factors. Basically, as I understand it, Bragg peaks depend on the symmetry ...
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Miller indices vs Laue indices?

I am looking at the difference between the Miller indices and Laue indices in crystal structures. I will denote the former by $hkl$ and the latter by $HKL$. I understand that $hkl$ must be coprime ...