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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Practical approach to reitveld refinement using xpert highscore

I have started using xpert highscore to perform reitveld refineent. Although I have getting good results, my agreement indices are hanging around the 4-5. I have been following MIT Prism's guide to ...
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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 ...
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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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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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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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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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, ...
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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 ...
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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 ...
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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: ...
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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,...
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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 ...
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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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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 ...
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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 ...
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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?
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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 $$\frac{1}{d_{hkl}^2}=\frac{h^2+k^2+l^2}{a^2}.$$ ...
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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 ...
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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 ...
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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.
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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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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 ...
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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 ...
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3 votes
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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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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 ...
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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 ...
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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 ...
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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_\...
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16 votes
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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 ...
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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 ...
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2 votes
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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. ...
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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 ...
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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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What is crystallographic equivalence?

I’ve learnt that in crystallography, there are many crystallographic directions that are “equivalent.” For example, in a cubic crystal system, the [011] and [110] and [101] directions are “...
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In powder x rd, if the crystals are randomly oriented ,why then do we get Debye rings and not random patterns?

In powder x-ray diffraction ,as I have learnt the sample is multi-crystalline.So if x-ray is diffracted through these randomly oriented crystal grains, aren't we supposed to get a random pattern?
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Why are certain reflections forbidden in body centered cubic and face centered cubic structures?

I know that for body centered cubic structures the allowed reflections only happen if h+k+l is even and reflections are forbidden is h+k+l is odd, and for basic face centered cubic structures (...
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5 votes
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Is the structure of a crystalized protein the native one?

When one finds the 3D structure of a protein by crystalizing it and then making a X-ray experiment, how does one know that the geometrical configuration of the crystal is the same (or even close) to ...
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Zinc oxide reduction in ethanol

I'm trying to prepare a ZnO thin film deposited on a glass substrate. The precursor solution prepared by sol gel process through dissolving 1 M zinc acetate dihydrate $\ce{Zn(CH_3COO)_2.2H_2O}$ in ...
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Why are X-rays used in crystallography?

Can any other wavelength of electromagnetic radiation be used? Why can't gamma radiation be used?
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Programs for chemical structure visualisation and drawing 2d and 3d [duplicate]

I want to create list of simple and useful software to draw molecules 2d and 3d with small description. Not necessary only freeware software. Also web-based services are interesting. Your help in ...
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Is there open source software for SEM EDX data analysis?

This can't be unique to me and would apply to anybody who has to use equipment in other departments has had departments move etc. What open source packages exist to read and potentially manipulate ...
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6 votes
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Angular dependence of x-ray and neutron scattering factors

Why are neutron scattering factors essentially independent of $2\theta$, whereas X-ray scattering factors drop off with increasing $2\theta$ ?
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Are molecular optimizations in quantum chemistry really in vacuum?

I know that Gaussian (or other quantum chemical packages) assumes the molecule is alone in vacuum, that is, the molecule doesn't interact with anything, when optimizing the molecule. But I've found ...
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How do you calculate a unit cell's dimensions from an XRD spectra?

My inorganic lab had us do an XRD measurement, but I've never been explained how to interpret the data. Question: Calculate the unit cell dimensions $a$, $b$, and $c$, for $\ce{YBa2Cu3O7}$ from ...
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