All Questions
19 questions
1
vote
0
answers
26
views
Unique lattice constant using X-ray diffraction
I recently learned about X-diffraction methods to analyse crystal lattices. One important law in this is the Bragg condition
$$\lambda = 2d\sin(\theta).$$
I understand that $d$ is the distance between ...
- 43
0
votes
0
answers
26
views
Why a crystal lattice with short axes would have a diffraction pattern in which spots would appear far apart using Bragg's law?
With the aid of Bragg's law, explain why a crystal lattice with short axes would have a diffraction pattern in which spots would appear far apart?
- 1
0
votes
1
answer
190
views
How to determine the interplanar distance from the Miller Indeces $(h k l)$ of different lattices
I know that for cubic unit cells, there is a simple correspondence between the interplanar distance and the Miller Indeces:
$d=\frac{1}{\sqrt{h^2 + k^2 + l^2}}$
What happens when we have more complex ...
- 548
2
votes
1
answer
339
views
How can the waves interfere in X-ray diffraction?
This is the popular diagram surrounding the Bragg's law for X ray diffraction:
But what I seem to not be able to understand is when they say that the reflected waves interact constructively to create ...
- 357
1
vote
2
answers
410
views
What is the catch behind the simple expression and explanation of Bragg's Law?
Consider how the topic of scattering by periodic crystal structures is covered in most books:
Start by treating the crystal structure as a periodic potential and use Fermi's Golden Rule to show that ...
- 1,461
1
vote
0
answers
32
views
Can raman be used to know the number of layers other than graphene?
I came across some paper where the number of layers of Graphene have been investigated by Raman spectroscopy. I found simulation websites https://instanano.com/characterization/calculator/raman/...
1
vote
0
answers
50
views
How does Bragg assigned $(h,k,l)$ values to planes in his paper?
I'm reading a Paper by Sir Lawrence Bragg on X-Ray Crystallography. I came across a paragraph which I don't understand after reading many times :
In the structural diagrams of sodium chloride on the ...
- 12.1k
0
votes
1
answer
856
views
No solution to Bragg's law?
Bragg's Law provides a description for the diffraction peaks we observe when x-rays are incident on a crystal structure. We observe these diffraction peaks because the wavelength of the incident x-...
- 1,599
1
vote
1
answer
75
views
Why is Bragg diffraction small-angle for thicker layers and/or larger molecules or unit cells? And wide-angle for small or shallow crystals?
It is easy to find equations that quantify this on the internet, but not an explanation as to why...
Also, does this apply to electrons and neutrons? Or just X-ray reflection/diffraction?
- 4,699
1
vote
1
answer
243
views
Why does the scattering wave vector and reciprocal lattice vector have to be the same?
In Introduction to Solid state physics 8th edition by Charles Kittel. The scattering amplitude is defined as, $$F=\int dV n_G exp[i(\bf{G-\Delta k}).\bf{r}]$$ where G is the reciprocal lattice vector ...
0
votes
1
answer
380
views
What is the interplanar distance? Bragg´s law [closed]
An X-ray (wavelength λ= 12.4 pm falls on a crystal)
The incidence angle (Θ) is the same as the dispersion angle = 16.6 degrees.
What is the interplanar distance if we observe the first order maximum?
...
1
vote
0
answers
147
views
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 ...
0
votes
1
answer
970
views
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 ...
- 1
1
vote
0
answers
196
views
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 ...
- 11
2
votes
1
answer
4k
views
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" ...
2
votes
0
answers
116
views
Why can we only observe Bragg Peaks when h, k and l are integers?
When studying Bragg's law, if we assume a cubic lattice, we can write the equation as
$$ \frac{2a \sin{\theta}}{\sqrt{h^2+k^2+l^2}} = n\lambda $$
Given a value for $\lambda$ , my professor said that ...
- 901
4
votes
0
answers
103
views
Neutron diffraction on Salty Ice VII
Can someone explain in layman's term how this figure shows the presence of Cl and Li ions in Ice VII ?
What can we deduce about the crystal from this data ?
The whole figure and caption are ...
- 685
3
votes
1
answer
1k
views
Getting the ($hkl$) Miller indices from the angle of incidence of a light ray
I was given an X-ray diffraction lab this week. We measured the count rate for different angles $2\theta$ of the rotation of the detector. From these measurements we plotted a graph of 2theta vs the ...
- 39
3
votes
4
answers
3k
views
Bragg diffraction and lattice planes
Crystalline substances show, for certain sharply defined wavelength and incident directions, very sharp peaks of scattered X-ray radiation.
From the illustration below we see that we get constructive ...
- 476