Questions tagged [crystallography]
For questions concerning crystalline structures and their properties.
81
questions
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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
64 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 ...
13
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2answers
948 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 ...
1
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1answer
46 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
48 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 ...
1
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0answers
32 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
50 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 ...
1
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1answer
63 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
112 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 ...
0
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2answers
60 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
36 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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0answers
31 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 ...
0
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1answer
56 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.
1
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2answers
60 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 ...
2
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0answers
50 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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0answers
76 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 ...
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2answers
94 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 ...
3
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0answers
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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: ...
3
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1answer
94 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
...
14
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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, ...
0
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0answers
33 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
91 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
584 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 ...
5
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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
53 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 ...
12
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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/...
3
votes
1answer
101 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 ...
2
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0answers
48 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
votes
0answers
150 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
votes
1answer
201 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
227 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 ...
0
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1answer
436 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
votes
1answer
140 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 ...
0
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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
votes
1answer
73 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?
...
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0answers
65 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
388 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 ...
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2answers
83 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
35 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
3k 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 ...
1
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1answer
121 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
458 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 ...
2
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1answer
71 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
41 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?
8
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1answer
283 views
How to dock aggregated structures comprised of “elementary” protein units like LEGO pieces?
There are proteins with intrinsic symmetries. For example:
I was wondering how to use transformations such as: rotations, translation, replications to construct possible structures using 2 types of ...
9
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1answer
2k views
How to make pyramid-shaped NaCl salt crystals
I'm attempting to make sea salt pyramids like the one below.
I understand this needs to be evaporated at a reasonable speed to stop the crystals forming a cube, as the when formed quickly, the edges ...
1
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0answers
142 views
Finding the percent void of the crystalline structure of NaCl [closed]
Find the percent of void in the crystal structure of $\ce{NaCl}$.
I am trying to calculate the percent void of the packing structure of $\ce{NaCl}$. Let's denote radius of anion as $r$, radius of ...
2
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0answers
36 views
What system of nomenclature can I use to indicate the positions of specific kinds of atoms of a surface reconstruction?
I was reading a journal based on SiC reconstructions, and they seem to mention that every dangling bond in the $(1\times 1)$ unreconstructed Si face or the $(0001)$ direction bonds up with a Si adatom ...
3
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0answers
42 views
Computational determination of unique adosrption sites
I'm not sure it's a chemistry question or physics question or math question. Since I'm active on this site, maybe someone here can point me in the right direction. I'm trying to enumerate all the ...
