Questions tagged [crystallography]
For questions concerning crystalline structures and their properties.
86
questions
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What is a material more easily cut than shattered? [closed]
I'm currently developing a sci-fi concept for animation which partially involves a typical "the earth has been overrun by XYZ" scenario.
One of the ideas for XYZ we're thinking of is a species of ...
0
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0answers
27 views
Visualization of all hcp voids
There are 12 tetrahedral voids and 6 octahedral voids in hcp unit cell but I can't find any image that can show all tetrahedral voids and all octahedral voids in hcp unit cell (the common picture in ...
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53 views
How to counter crust formation when crystallizing NaCl on the liquid-air interface?
Saturated sodium chloride solutions are evaporated at elevated temperature. The aim of evaporation is to produce hollow pyramid salt crystals. Temperatures used range from 65°C to 85°C. With 80°C ...
1
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1answer
78 views
How strong are molecular bonds in layman's terms?
Suppose you had a single sheet of graphite the size of an A4 page. What would it feel like to handle it?
Would your fingers instantly tear through it as you tried to grasp it?
Could you punch your ...
2
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0answers
50 views
Sources for files for testing a thermal ellipsoid (ORTEP) program
I am trying to reimplement the functionality of the classical program ORTEP for producing thermal ellipsoid plots of a crystal/molecule in a modern computer language. Unfortunately, I am having ...
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39 views
Pncn space group diagram
I'm trying to make a diagram of the Pncn space group.
Firstly, I know that this space group belongs to the orthorhombic system and derives from the point group (2/m 2/m 2/m).
Therefore, although the ...
0
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1answer
68 views
Symmetry Space Group Diagram
I am doing an introductory course to Crystallography and I have found in the following web page: http://pd.chem.ucl.ac.uk/pdnn/symm3/sgmonoc.htm a guide for the elaboration of the diagrams of the ...
14
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2answers
993 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 ...
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1answer
49 views
Are there examples of crystals with random but static mixtures of two unit cell configurations?
The image in this question turned out to probably be wrong, but it still makes me wonder. Are there examples of crystals where the atoms within a unit cell can have two (or more) different ...
2
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0answers
61 views
Crystallographic terminology associated with the honeycomb structure
I'm trying to quickly learn basic crystallographic principles in 2D under pressure (it's me whose under pressure, not the lattice) so I'm checking many sources to find those that "speak to me" the ...
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159 views
Calculating distance between adjacent planes (hkl) in a simple cubic crystal
My textbook says the following in a section on Miller indices:
Adjacent planes $(hkl)$ in a simple cubic crystal are spaced a distance $d_{hkl}$ from each other, with $d_{hkl}$ given by:
$$d_{...
2
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1answer
58 views
Miller indices: How does one translates the orientation to the origin of the unit cell?
In a section discussing Miller indices, my textbook says the following:
The rules for determining the Miller indices of a direction or an orientation in a crystal are as follows: translate the ...
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1answer
78 views
How do I view a DSN6 file as text?
I am trying to isolate certain pieces of information within a dsn6 file. Specifically, I want to find the electron density around two atoms within a protein. I want to then run a python code to ...
3
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1answer
134 views
Space groups: Herman-Maugin notation, diagrams and Wyckoff positions
I am currently taking an Introduction to Crystallography course. After studying and understanding the punctual symmetry groups (2mm, 4/m 2/m 2/m, 32,...), the flat groups and the diverse elements of ...
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2answers
64 views
How can I find the smaller symmetric structure from big crystal unit cell?
I have Pyrope (Mg3Al2(SiO4)3) crystal structure, downloaded from materialsproject:
https://materialsproject.org/materials/mp-6073/#
It appeared as triclinic cell, but if you download CIF file and ...
2
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1answer
37 views
Why is the order of reflection simplified to n = 1?
My professor told us that for the sake of simplicity, we will assume that the order of reflection for Braggs' Law is always equal to 1 but failed to explain why. Is it because d(h,k,l) for materials ...
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33 views
How do blue shifts in Raman spectra indicate a co-crystalline compound?
The short conference paper The Acetylene-Butane Co-Crystal: A Potentially Abundant Molecular Mineral on Titan (mentioned in EurekaAlert's 'Bathtub rings' around Titan's lakes might be made of alien ...
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1answer
129 views
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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2answers
69 views
Why is Libethenite (Cu2(OH)PO4) color green?
It is not a complex compound and the copper atom is not oxidized so I'm wondering how does its color change. The book mentioned that at favorable conditions, adding water in Copper phosphate, which is ...
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0answers
64 views
Understanding lattice matching of graphene on silver (111) crystal surface and meaning of the √3 x √3 lattice?
Figure 1 in Ivor Lončarić and Vito Despoja, Phys. Rev. B 90, 075414 Benchmarking van der Waals functionals with noncontact RPA calculations on graphene-Ag(111) (available in Researchgate) shows a ...
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201 views
Silver (111) surface structure, and is bulk structure body-center or face-center cubic?
I'd like to understand the atomic arrangement is on a silver (111) surface.
Step 1 would be to find out the bulk crystal structure.
Wikipedia lists silver as face-center cubic (fcc) here and here ...
0
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2answers
513 views
Relation between size of ion and hydration energy [closed]
Suppose I take 1 tablespoon of an ionic crystal and put it in excess water. We know that shall the hydration energy of the crystal be more than the lattice energy, the crystal will separate in ions ...
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0answers
41 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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1answer
192 views
Space group diagram
If you give me the name of a certain space group, for example, the P222 (orthorhombic system). How could I construct the following diagram?
Image source: http://img.chem.ucl.ac.uk/sgp/large/sgp.htm
...
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2answers
3k views
Are there any crystals that are theoretically possible, but haven't yet been made?
Are there any crystals (that exist at standard temperature and pressure) that are theoretically possible, but haven't yet been made?
For example, the predicted requirements for temperature, pressure, ...
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47 views
Explanation of metallic crystal structures using orbitals and electron configuration
There has to be a direct relation between metallic crystal structure formation and electrons in orbitals. For instance, we know that Fe2+ forms body centered cubic or bcc structure with the ...
6
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1answer
116 views
Are electronic descalers a scam?
It seems there are some electronic kits sold around nowadays by major retailers (e.g., Home Depot and Amazon) claimed to remove built-up scale from water pipes.
But, do they actually work? If so, ...
4
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2answers
725 views
Sulfuric acid symmetry point group
On the following page: https://cccbdb.nist.gov/pglist.asp It appears that the point symmetry group of sulphuric acid is $C_2$. I know that $C_2$ means that there is an axis of symmetry of order 2 (180 ...
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0answers
55 views
Effect of spontaneous transmutation of atom in crystal
What happens to a compound when one of its atoms changes via spontaneous nuclear reaction to an atom with very different bonding? For example, beryllium-7 turns into lithium-7 with a half-life of 53 ...
1
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1answer
57 views
Lattice type from image
What type of 2D lattice is depicted in the image shown below? Is it possible to determine without knowing the length of the unit vectors and the angles in between them? I'm confused because it ...
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4answers
1k views
What is the smallest molar volume?
I wondered how small a volume a mole of material could occupy, so I started with carbon, which would need 12 grams. That's 60 carats, and there happens to be a famous 60 carat diamond.
If my density/...
5
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1answer
120 views
Testing for asbestos using readily available chemicals and tools?
Given that it is difficult to determine who is telling the truth in the recent claim that J&J covered up finding asbestos in their powder, is there any chemical test that we can perform on our own ...
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52 views
Reading Stereographs
On an old paper, I found an interesting representation of some symmetry operations: stereographs.
Online I found a set of symmetry operations and related stereographs (see: http://newton.ex.ac.uk/...
3
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0answers
151 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 ...
2
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1answer
253 views
How to get ionic radii for coordination number 12?
I am studying $\ce{ABX3}$ perovskites, and I would like to calculate Goldschmidt tolerance factors for them. The $\ce{A}$ sites in these materials have a coordination number $12$.
The Shannon's ...
4
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1answer
335 views
What is the Crystal System of MoS2?
I'm confused about the crystal system of MoS2.
In the case of the monolayer MoS2, it has 3-fold rotation symmetry when viewed from the top of its unit cell (c-axis). Even in the case of bulk (AB ...
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1answer
816 views
What about Miller Indices of planes passing through origin?
For Miller Indices of planes if we encounter a case where the plane passes through the origin then I have heard that the only remedy can be arrived by shifting the origin to a different point.However ...
5
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1answer
180 views
What is the diagram of the roto-inversion of $\bar 6$?
Using the standard way of representation:
Here we have a rotation followed by an inversion (technically called 'rotational inversion'). So as to represent it, what I have done is:
1) Both rotation ...
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1answer
1k views
Solubility curve for sodium tetraborate in water
What is the solubility curve for sodium tetraborate decahydrate ($\ce{Na2[B4O5(OH)4]·8H2O}$), otherwise known as borax, in water ($\ce{H2O}$)?
Additionally, what is the solubility of the ...
3
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1answer
76 views
Does a molecule need to be placed symmetrically in the unit cell?
I was watching an OCW by MIT (3.091X) on solid state. My previous notion of lattice point and unit cell got shattered after this example.
Where are the unit cell and lattice points in this picture?
...
3
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1answer
98 views
Rietveld (FullProf) general background function
I was reading through Eric Mittemeijer's book 'Modern Diffraction Methods' when I found the following statement in the Rietveld chapter by Robert Dinnebier.
It is common practice to use orthogonal ...
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1answer
534 views
Length of NaH bond from the edge length of unit cell
If the edge length of $\ce{NaH}$ unit cell is $\pu{488 pm}$, what is the length in $\pu{pm}$ of an $\ce{NaH}$ bond? The answer is $\pu{244 pm}$, I thought that $d = 2 \sqrt{2}\times r$ , do you not ...
3
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2answers
137 views
Is there a piece of software that can help me see the (hkl) planes in a crystal lattice?
I am doing research with calcium carbonate structures. I need a way in which I can familiarize myself with the lattice structure of calcium carbonate polymorphs, especially calcite.
I really struggle ...
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0answers
36 views
Rietveld refinement “fronting” of peak signal
I was trying to refine a crystal structure using Rietveld refinement yesterday. The crystal structure is already known for a related compound and the powder pattern seems to show a phase pure compound....
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2answers
4k views
Calculate the third and fourth nearest neighbours in bcc
My textbook has given data for third and fourth nearest neighbours to be 12 and 8 with distances $\sqrt{2}a$ and $\frac{\sqrt{11}a}{2}$.
I have been able to calculate for the first and second ...
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1answer
145 views
Why lattice constant (unit cell) is always a parallelepiped?
Wikipedia defines lattice constant as physical dimension of unit cells in a crystal lattice.
Unit cell is defined as:
The unit cell is defined as the smallest repeating unit having the
full ...
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0answers
541 views
Body centered cubic lattice vs Primitive cubic unit cell
I was reading about Bravias lattices(cubic crystal system) when got confused about an article in my book.
Please refer to Counting body center as lattice point when basis consists of 2 atoms.
The ...
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1answer
83 views
Crystal structure database search for space groups
I'm usually using databases like the Springer Materials site or the free Crystallography Open Database to get crystal structure data. But none of these offers the possibility to search for all entries ...
1
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1answer
18 views
Electrochemical manufacturing of small metal components
Metal crystals easily can be grown via electrochemical pathways. Copper is a great example of this. I recently had an idea of growing those crystals in controlled ways (i.e.: surrounding the electrode ...
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0answers
43 views
Single Crystalline Thin Films is detect by GIXRD? [closed]
I understand epitaxal thin film, have lattice match with substrate.
But what about those films that doesnt match but have only one XRD peak? Is this proof of single crystale thin film?
