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Questions tagged [x-ray-diffraction]

X-ray diffraction is a method to obtain the crystal structure of a compound. This tag is also appropriate for x-ray powder diffraction.

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Ideal Chi-squared for X-ray pattern Le Bail fit

I have made a potentially novel solid state phase. I know the general parameters it should have, and have been trying to Le Bail fit XRD data about this phase prior to a synchrotron run in May. I have ...
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Small-Angle X-Ray Scattering of Bulk Polymers

Does anyone have any recommendations on how to get useful information from SAXS of polymers when the system is not dilute? This is the type of data we're working with: My understanding is that since ...
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Negative absorption coefficient

What does a negative absorption coefficient mean? In detail - I participated in a Synchrotron virtual laboratory. I have to analyze the results and understand what a negative absorption coefficient ...
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XRD experiment: how to interpret data and solve crystal structure from 2theta vs intensity values

I have just performed an XRD (X ray diffraction) experiment (powder), but the XRD machine I have used is not able to describe crystal data, I have $2\theta$ and intensity in arbitrary units in a UXD ...
Ștefan Dumitrescu's user avatar
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Crystal lattice structure from single crystal x-ray diffraction pattern

Is there a good reference describing the inverse problem of determining the crystal lattice, unit cell etc., from a single crystal x-ray diffraction pattern and chemical composition? I am looking for ...
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Converting Quartz data from one (P3221) space group to another (P3121)

For my studies, I’ve done a lot of work on coal fly ash QXRD QPA on TOPAS which has been a fun and interesting challenge. Apart from theory reviewing, a lot of my learning so far has come from a prior ...
Hendrix13's user avatar
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Direction of electron flow in X-ray Tube in X-ray Crystallography

In X-ray crystallography, X-ray tube may be used to generate X-ray. The set-up is the following: Here it shows the electron beam goes from cathode to anode. If anode is the negative electrode, why ...
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2 answers
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What is the difference between alloying and doping? [closed]

When compared to doping, how is alloying different? What modifications to the structure are brought about by both of these?
Udeshwari's user avatar
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How do different x-ray tube emission profiles (i.e copper vs cobalt sources) affect XRD samples containing iron (results included)?

Background: I'm a student and have recently done some XRD on some iron ore mine tailings which came from an Australian mine tailings storage dam. The redness in colour and industry source led me to ...
Hendrix13's user avatar
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1 answer
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Why and how are mullites (and in extension solid solutions) formed and how are their formulas conceived as opposed to regular crystalline solids?

From doing more Phase ID for XRD on aluminosilicate based coal fly ash samples, I've seen mullite phases appear a few times which have the non-stoichiometric chemical formula $Al_{4+2_x}Si_{2-2x}O_{10-...
Hendrix13's user avatar
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What are some good synthetic samples I can make myself to start getting better at Quantitative X-Ray Diffraction?

I'm a student wanting to become an expert in quantitative X-Ray Diffraction (QXRD) to determine the wt%s of both crystalline and amorphous phases in a solid specimen. At my university I have access to ...
Hendrix13's user avatar
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What is a good strategy for fully quantitative X-Ray Diffraction on coal fly ashes?

I am having some trouble with fully quantitative phase identification of coal fly ashes using x-ray diffraction (XRD). Here follows some basic information about the experiment: -- ...
Hendrix13's user avatar
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4 votes
1 answer
423 views

Integrating structural information to carry out Rietveld refinement

I have just started using Xpert highscore for analyzing my XRD raw data. I have access to PDF2 database(Powder diffraction file) using my university license. I have also just started using reitveld ...
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Navigating through the various characterisation technique?

We synthesis a lot of ceramic catalysts. For a long time now, we are facing problems in accurately and efficiently characterising the synthesized powders. We have identified the main problems as ...
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What do sequence numbers in PDB files actually mean and why don't they match the sequence?

I am studying the 3D structure of the LDH from x-ray crystallographic imaging I was pointed to from Is there any stereospecific enzyme in PDB that catalyzes an anabolic reaction and has an entry ...
Gunther Schadow's user avatar
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2 answers
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LEED - determining surface structures

How can one describe surface structures (before and after adsorption)? I understand the diffraction theory but I have never really tried to determine the structures of samples by myself. LEED (low ...
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1 answer
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How to identify 'water' mistakes in protein crystal structures: Are B-factors and occupancy good indicators?

When solving the structure of a protein from diffraction data (x-ray crystallography), it can sometimes be difficult know what should be modelled into small spheres of electron density that are not ...
CuriousTree's user avatar
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Rietveld Refinement: Calculated Intensities far lower than observed for a small selection of miller indices

I'm performing a Rietveld Refinement in excel of an I4/mcm material CeAlO3. The fit is very good for most peaks but on a few, I'm coming up very short on the intensities. Could this be due to a local ...
Daddy Devito's user avatar
2 votes
2 answers
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Find atomic radius from angle, wavelength, (311) plane and FCC structure

I've worked this problem and seem to be off by a factor of $2$ somehow. From Callister, 6th edition, problem 3.56W (but I don't have access to the "W" web material that actually explains ...
RobertTheTutor's user avatar
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X-ray Diffraction Lattice Spacing

I have crystal structure data which I have indexed. I am able to index the (010) (100) (011) (110) and (111) planes. Is there a straightforward method to calculate the a,b,c lattice constants based ...
Tristan Maxson's user avatar
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What do we know about the structure of the amylopectin iodine complex?

I am studying a method of finding the ratio between amylose and amylopectin using the difference in color of the amylose-iodine complex(blue) and the amylopectin-iodine complex (red/brown). Through ...
jettosutorimu's user avatar
2 votes
1 answer
467 views

Why is the disordered CuAu structure more stable at high temperatures?

I know that the disordered CuAu structure is based around FCC whereas the ordered CuAu structure is tetragonal. Why would the FCC structure be more stable at high temperatures? For context, I was ...
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4 votes
1 answer
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Getting an “index” of 7 for a set of powder diffraction data

I tried to index powder diffractogram from the following problem: A metal (of density $\pu{0.862 g cm^-3})$ gives the following powder X-ray diffraction data $(\lambda = \pu{1.5418 Å}).$ $$2\theta \...
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3 answers
193 views

Am I visualizing/understanding atomic form factor correctly?

I'm having difficulty visualizing the concept of atomic form factor or atomic scattering factor as it has been presented in a chemistry course on X-ray crystallography that I'm taking. At the moment, ...
vinyl_chloride's user avatar
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1 answer
238 views

What is the precision of intensity data in XRD measurement?

I made some relative crystallinity measurements on a zeolite (crystalline aluminosilicate). Which is measured for a specific peak area and compared with a reference sample. The XRD of powder patterns ...
marietiara's user avatar
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How does X-Ray Crystallography determine the components (as opposed to the structure) of a molecule?

Thanks for some online resources (i.e. here) I have an understanding of what X-Ray Crystallography does. By blasting X-Rays at a crystal and recording the scattering patterns on a plate behind the ...
CodyBugstein's user avatar
6 votes
1 answer
179 views

Can we observe the shapes of MOs? [duplicate]

Condensed question formulation: Is there an experimental method to directly visualise the 3D form of a MO wave function, or at least the electron density associated with it? Full statement: ...
aureolin's user avatar
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Analyzing alternating metals in a polymer matrix with 1 micrometer depth and only 10% metal

This is a theoretical question that I am struggling to get started on for a seminar discussion. If you were attempting to design an instrument with all the basic components (source, analyzer, detector,...
Harley McFarlen's user avatar
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209 views

How will the X ray diffraction pattern change if the crystal changes its lattice structure

(I asked this question on another community without getting much help there,I hence post it here as it may be more of a chemistry question. I apologize if my question has an obvious answer, I'm only a ...
Kashmiri's user avatar
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1 answer
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How to create .CIF file from DRX data in a paper, for compound not found in crystallographic database

I tried to recover a .CIF file with the crystal structure for the compound discussed in this 2006 paper, strontium hydroxide octahydrate - $\ce{Sr(OH)2·8H2O}$ - from Cambridge Crystallographic Data ...
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1 answer
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XRD: Can stacking faults cause pseudo-centring?

Consider a cP lattice with a = 10 Å and an octahedron residing on each of the unit cell's vertices as shown below: The maximum symmetry will be Pm-3 m. Now, let's consider there are stacking defects ...
tstone-1's user avatar
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1 answer
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XRD Peaks in databases

I had a look at the JCPDS card of BiOCl and saw that there were very small peaks (such as 0.1 percent relative intensity) that I think wouldn't be observed in XRD pattern, they would just blend in ...
Aleksejus Pacalovas's user avatar
4 votes
1 answer
133 views

Crystal structures of heaviest nuclides' compounds

What is the heaviest element of the periodic table for which there is a compound whose crystal structure has been completely resolved by X-ray diffraction?
Antonio Gamiz Delgado's user avatar
1 vote
2 answers
369 views

What is the origin of the Quadratic factor in calculation of XRD peaks?

Whenever we are to calculate the d-spacing(for cubic system) in XRD peaks with reference to Quadratic Factors we do that with the help of the formula $$\frac{1}{d_{hkl}^2}=\frac{h^2+k^2+l^2}{a^2}.$$ ...
user586228's user avatar
16 votes
2 answers
2k views

How were x-ray diffraction patterns deciphered before computers?

I know the general idea behind x-ray crystallography is to take a high quality crystal and place it in the path of an x-ray beam. Areas of high electron density will diffract the beam and lead to ...
Joe's user avatar
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What's the definition of multi phase materials? Does it mean the different phases represent different materials?

I'm from a CS background and just trying to understand the real meaning behind multi phase materials. Following is the experiment which drove me towards this question. With the help of DFT and ...
Achintha Ihalage's user avatar
0 votes
1 answer
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What kind of isomerism does Ni(PPh3)2Cl2 have and what is their IUPAC name? [duplicate]

I know that there are 2 isomers that $\ce{Ni(PPh3)2Cl2}$ have and they exist in equilibrium. I am tempted to name them cis- and trans- but it does not sound right.
Kent de los Reyes's user avatar
4 votes
2 answers
272 views

What is "detwinning" as a 2D crystallography technique?

The Phys.org article Iron selenide revealed as 'garden-variety iron-based superconductor' is quoted below. Normally I would hesitate to quote so much but in this case it all seems germane. Question: ...
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2 votes
2 answers
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Obtaining atomic form factor from electron density?

I know that atomic form factors for x-ray scattering are obtained by Fourier transform of the electronic charge density. I am looking for a citable elementary source (book, review, article) which ...
R.U.'s user avatar
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2 votes
0 answers
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XRD-Amorphous materials

I am interested in sealing some air-sensitive samples inside of xrd-amorphous material to allow for XRD and hopefully XRD-texturing analysis. Of course, Kapton is the common material used for this ...
User2341's user avatar
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3 votes
1 answer
195 views

X-ray structure analysis mirrored coordinates?

How to ensure, that X-ray crystallography structure analysis was done right to provide correct, non-mirrored atomic coordinates? Example: Following Wikipedia image, is generated from data taken from ...
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1 vote
1 answer
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Why are powder XRD axes sometimes plotted in reverse?

Just plotting some powder XRD data and I wanted to know why the axes in some of the literature that I'm looking at is plotted in reverse. Is there a reason it starts at 60 Degrees (2 theta) and then ...
user11585's user avatar
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1 answer
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Amorphous conductor transparent to XRD

I want to conduct in-situ XRD of a cathode in my battery using this coin cell with a kapton viewing window. I assume this cell configuration is the best I can find for my purpose, and that I can't ...
User2341's user avatar
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2 votes
0 answers
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What is the crystal structure for a crystal where the ratio of the squares of the angle peaks is 0.825?

I followed this and it gives an example of how to identify a crystal structure using XRD data. I have an unknown alkali halide where two peaks were found at $2\theta =25.66$ and $2\theta = 28.3$. I ...
whatwhatwhat's user avatar
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0 answers
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What can be concluded from two different values for the interplanar distance between planes of atoms in an X-Ray diffraction experiment?

I analyzed an unknown Alkali Halide crystal using x-rays from a copper source. I need to find the d-spacing for this crystal, i.e. the interplanar distance between planes of atoms. I found my $K_\...
whatwhatwhat's user avatar
17 votes
2 answers
1k views

Why is crystallography still used in some cases for small molecule structure determination?

I was wondering for some time why in some cases x-ray crystallography and not NMR is used for structure determination of small molecules? Does crystallization maybe require a smaller amount of the ...
geox19's user avatar
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4 votes
1 answer
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Single crystal x-ray diffraction experiment backwards: from CIF to genuine set of raw data without performing actual experiment

Single crystal x-ray diffraction stands among the most complex yet trustworthy analytical techniques when it comes to structure determination of solids. But how hard it would be to simulate(fake) the ...
andselisk's user avatar
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2 votes
2 answers
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How can I solve a non-cubic crystal structure?

Say I want to solve the crystal structure of barium sulfate, and I want to not only determine crystal type and the lattice parameter, but also the orientation of the oxygen atoms on the sulfate anion. ...
user2945985's user avatar
9 votes
3 answers
1k views

What is the quantum mechanical explanation of X-ray diffraction?

One topic in crystallography that I've found a surprising dearth of information on is what the fundamental interaction behind the interaction of the X-ray and atom. Pretty much every book just treats ...
Canageek's user avatar
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4 votes
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Second Peak in X-Ray Diffraction Pattern of bcc Metal

By Bragg’s law, $$2d\sin\theta=n\lambda$$ and $$d=\frac{a}{\sqrt{h^2+k^2+l^2}}$$ Combining the two gives: $$\sin\theta=\frac{n\lambda\sqrt{h^2+k^2+l^2}}{2a}$$ By the reflection rule for bcc, there ...
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