Questions tagged [crystal-structure]
In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid.
551
questions
4
votes
2
answers
653
views
Can “hydrates” of crystals form with other molecules?
It is well known that copper sulfate, sodium sulfate, et al crystallize with 5,10 water molecules of hydration, locked in their crystal lattices. Is it possible to have other molecules instead of ...
- 57
-2
votes
1
answer
23
views
Formation of cocrystals troubleshootin
In cocrystal formation what would the possible reason be for the precipitation of an amorphus oily precipitate not suitable for PXRD? Solvent was DMF and the reagent were L-thyroxine and ...
4
votes
6
answers
605
views
Does an ionic bond have a dipole?
Is an ionic compound like NaCl considered a dipole? It has a positive side (Na+) and a negative side (Cl-). Or is it true that an ionic bond does not have a dipole because a dipole is, by definition, ...
3
votes
2
answers
104
views
Crystal structure of tin tetraiodide
I was looking at the molecule of $\ce{SnI4}$ and how its structure looks like in its crystal lattice:
Wikipedia.de says its crystal lattice is of the fcc (ccp) type (for the iodine atoms), which ...
- 267
10
votes
1
answer
716
views
Why does this lysozyme powder not look crystalline?
I am very new to protein crystallography and visualization. I have been asked to take photos through an optical microscope of the lysozyme powder directly as-is from the supplier. I suspended some of ...
- 111
4
votes
1
answer
448
views
Why does KCl have FCC structure instead of BCC?
I have this table here.
\begin{array} {|r|r|}\hline \text{Radius Ratio} & \text{Coordination number} & \text{Type of Void} \\ \hline <0.155 & 2 & \text{Linear} \\ \hline 0.155-0....
4
votes
2
answers
473
views
What determines how easily a gas can diffuse into a crystal structure?
I have been told by a metallurgist that the reason a factory oxidizes the iron oxides in ilmenite before reducing them down to pure iron, is that the the products of this have a more spacious crystal ...
- 301
-2
votes
1
answer
64
views
How to express the lattice parameter of NaCl in terms of ionic radii? [closed]
In the $\ce{NaCl}$ lattice, $\ce{Cl^-}$ takes the FCC configuration, and all the voids at the edge and body center are filled by $\ce{Na^+}.$ So, do we calculate the edge length of unit cell $a$ as
$$...
0
votes
0
answers
40
views
Copper sulfate pentahydrate crystal structure [duplicate]
I am interested in what exactly the structure of copper sulfate pentahydrate crystal is like. In the wikipedia, it consists of copper and sulfate strand with 4 water attached to each of the copper ...
- 9
3
votes
1
answer
151
views
Temperature Dependence of Crystal Formation in Storm Glass
The storm glass is an interesting historical device which claims to be able to predict the weather (for example, clear liquid implies fair weather, murky liquid implies rainy weather and large flaky ...
- 147
-3
votes
1
answer
87
views
Is this a Pyrite crystal cube? [closed]
There is a metallic shine on it that does not clearly show in the photo
This cube weighs 458g
Dimensions: 55mm H x 45mm W x 39mm D
Is this a Pyrite cube?
Thank you
- 13
3
votes
0
answers
58
views
Why does gallium expand on solidification
I've heard that Ga exist as Ga2 molecules in its crystal lattice. Does that have anything to do with expansion of Ga while solidifying? Why and how does it actually expand?
1
vote
0
answers
57
views
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 ...
- 484
7
votes
1
answer
333
views
What does the 'S' stand for in base-centered cubic crystals and Bravais lattices?
The 'I' used for body-centered systems is for the German word Innenzentriert and the 'F' for face-centered is for Flächenzentriert, also German but what about the 'S' for a, b, or c base-centered ...
- 1,797
0
votes
0
answers
15
views
The existence of anti-phase boundaries (APBs) in defective crystalline materials
The existence of anti-phase domain boundaries (APBs) in polycrystalline materials is usually established by electron microscopic techniques (SEM/TEM) [1] and is also discussed in diffraction data ...
2
votes
1
answer
60
views
Why are certain lattices compatible with only certain point groups and not all point groups?
I will limit this discussion to 2 dimensions for ease of intuition. My understanding of the 17 crystallographic plane groups is that these 17 groups represent all the possible symmetry groups of any ...
- 241
4
votes
2
answers
178
views
Crystal structures exhibiting dimeric arrangement of tetrahedrally coordinated cations
I am looking for inorganic crystal structures that exhibit tetrahedrally coordinated cations arranged in a vertex-sharing dimer arrangement, where the cation - shared vertex - cation angle is close to ...
6
votes
1
answer
385
views
Do hydration (as in "solvation") and "hydration" of salts refer to the same phenomenon?
I've come across two use cases of the word "hydration", presented to me as distinct topics:
Solvation is the process of reorganizing solvent and solute molecules into solvation complexes ...
- 91
4
votes
2
answers
540
views
What do consecutive letters A and B in the 4th column of PDB file signify?
What do the consecutive A and B in the 4th column identify in a PDB file downloaded from rcsb.org?
The molecule name is 3CZ3 (...
- 41
0
votes
0
answers
52
views
Endothermic peak in DSC
I have an endothermic peak, with no mass loss and no change in (organic) crystal structure (monitored by vt-pxrd). What can cause such effect? Also, excluding the options of impurities or instrumental ...
- 9
8
votes
1
answer
303
views
Why does zircon hate lead? How do these tiny crystals so effectively exclude lead atoms during formation enabling accurate uranium-lead (U-Pb) dating?
Background
From the December 29, 2022 NPR article To peer into Earth's deep time, meet a hardy mineral known as the Time Lord:
"(Zircons) are really the best markers of Earth's time, or the ...
- 5,720
0
votes
1
answer
63
views
Why does FCC crystalline forms form hexagonal crystalline structures during CVD?
During the CVD process, Copper and Nickel which are both Face Centered Cubic crystalline structures are used as substrates for shaping hexagonal atomic structures such as graphene and hexagonal Boron-...
- 41
-1
votes
1
answer
74
views
Is the number of atoms per unit cell for Hexagonal Close-packed (HCP) really 6?
I am questioning whether the conventional N=6 for HCP is accurate. This question is spawned from an image in ZYbooks Material Science and Engineering textbook by Callister and Rethwisch, where they ...
- 1
4
votes
1
answer
128
views
Role of spin of electron in splitting of orbitals
What will happen if there are electrons with opposite spins present in the orbitals of ligand and metal atom during the splitting of orbitals in crystal field splitting?
Magnetic fields of two ...
3
votes
1
answer
1k
views
Silicon crystal orientation
I'm confused about how [110] direction is determined for (100), (110) or (111) wafers. I found a book chapter which just confused me even more. From the image below, I understand how [110] is ...
- 61
1
vote
0
answers
63
views
Why are crystals of carboxylic acid fluffy
I'm an undergrad student and we recently performed saponification of esters which resulted in the formation of carboxylic acid which we had isolated out of the reaction mixture.
After ...
- 29
0
votes
0
answers
24
views
Relating the diffraction angle to the angle from the “zeroth order beam”
What I’ve been asked relates to diffraction from scattering atoms in materials with periodic atom array structures.
“For two scattered in a beam of radiation that are a distance d apart, show that the ...
- 39
-2
votes
2
answers
269
views
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?
3
votes
1
answer
246
views
Relation between symmetry of a reciprocal vector and lattice planes perpendicular to it
What is the relation the symmetry of a high-symmetry point in the first Brillouin zone and lattice planes perpendicular to it? Are the two symmetries equivalent?
I have this question because I want to ...
- 273
4
votes
1
answer
241
views
Line Entry system like SMILES for metals?
SMILES is not designed for metallic compounds.
Is there a similar ASCII line entry notation for metallic compounds, including repeating structure in space, &c.?
- 51
2
votes
1
answer
52
views
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 $Al_{4+2_x}Si_{2-2x}O_{10-...
- 484
0
votes
1
answer
67
views
Is it possible for an appropriately vaporized crystal to have vapor properties in any way related to it's crystal? [closed]
Is it possible for an appropriately vaporized$^{1}$ crystal to have vapor properties in any way$^{2}$ related to it's crystal, or unique to the fact it was a crystal in it's previous phase?
The ...
- 111
0
votes
0
answers
66
views
Database of atomic crystal structure data or images of rocks and minerals?
I am looking for crystal structure images so I can redraw them in a nice form. However, I don't seem to find much searching Google.
Perhaps this is a slightly better example (searching for Quartz ...
- 103
8
votes
1
answer
171
views
Does water expand on freezing more than any other known substance?
Several substances expand on freezing. Gallium expands 3.1% and bismuth 3.3%. However, both of these are much less than water which expands 9%. Is there any substance that expands more than 9% on ...
- 784
0
votes
1
answer
48
views
What are good ways to anticipate co-crystalization of different metal ions?
What rationale (purely theoretical/assumptive, or known by experience / backed by evidence) would you use in an attempt to effectively anticipate which other metal or elemental ions are most likely to ...
- 1,067
4
votes
0
answers
44
views
Why is reported effective pore size smaller that the one declared in the name of the molecular sieve type X?
The molecular sieve type is often coded with <number><letter> combination, where <number> specifies the pore ...
- 37.3k
0
votes
1
answer
98
views
Are there tools or algorithms to detect organic molecules from 3D crystal structures?
The task I'm thinking of is to detect entire molecules from structures, such as in a crystallographic information file (CIF) or from the XYZ file generated in a molecular dynamics simulation. ...
- 76
-2
votes
1
answer
63
views
What is the structure of hydrated beryllium chloride [closed]
Is there water of crystallization or does water act as ligand? Also Be2+ is smaller than Li 2+ then why Li2+ has only 2 water molecules as ligands
- 340
6
votes
1
answer
602
views
Number of bridge oxygen atoms in a silicate mineral
Total number of oxygen atom(s) which act(s) as bridge between any two silicon atoms in a mineral with composition $\ce{MM’Si3O_x}$ $(\ce{M}$ is the divalent metal ion and $\ce{M’}$ is the tetravalent ...
- 342
0
votes
0
answers
45
views
Data for Madelung Constants
Where can I find data for the Madelung constants for various ionic compounds? Specifically, I am looking at silicon tetrachloride, yttrium (III) chloride, zirconium (IV) oxynitrate hydrate, niobium (V)...
2
votes
0
answers
51
views
How do other elements fit into a diamond's carbon lattice (e.g. nitrogen in yellow diamonds)
Traditional pure-carbon diamonds have a simple structure (tetrahedral, if I'm not mistaken). But common types of diamonds have other elements within them. For example, yellow diamond has nitrogen in ...
- 121
0
votes
2
answers
133
views
Two atoms exist in the same coordinate position in the lattice?
I am trying to simulate the properties of FeF3(H2O)3, so I download its crystal structure file from Crystallography Open Database, but it seems that in the lattice, ...
- 161
-2
votes
1
answer
846
views
In calculating the radius ratio in a tetrahedral site in an FCC lattice, why do we take tetrahedral void in the middle of the body diagonal line? [closed]
When calculating the ratio of cation / the ratio of anion in a Tetrahedral system in an FCC lattice, why do we take the void to be in the center instead of it being √3a/4 from the corner.
-1
votes
2
answers
104
views
Why does density decrease when pressure is increased on an NaCl type lattice?
I was told that the effect of pressure on an NaCl type structure would make the atoms come closer and therefore change the type to CsCl type making Z (no of atoms per unit cell) go down, hence density ...
- 19
4
votes
1
answer
736
views
Why is there a difference in crystal shapes of sodium chloride (NaCl) and potassium chloride (KCl)?
According to Sodium chloride and Potassium chloride:
Sodium chloride (NaCl) crystallizes, among various other shapes, into octahedron and tetragonal pyramid shapes which are absent in potassium ...
- 69
2
votes
1
answer
216
views
How to find the standard deviations of lattice parameters after Rietveld refinement with GSASII?
I am trying to learn how to use GSASII. It is different from GSAS/EXPGUI, so I feel hard to find some information from GSASII interface. I want to find what are the values for the standard deviations ...
- 21
3
votes
0
answers
44
views
Radius ratio of capped octahedral coordination (CN=7)
I was asked to work out the Radius ratio of capped octahedral coordination when CN = 7. How to define a capped octahedral? Is there any restrictions on the lengths of the edges or the distances of the ...
4
votes
2
answers
309
views
Why aren't ionic crystals stronger than diamond?
If ionic bonds are stronger than covalent bonds, then why aren't ionic crystals stronger than diamond, which is bonded by covalent bonds?
Diamond has tetrahedral structure with carbons forming ...
- 59
6
votes
1
answer
454
views
Why does Samarium have such a large c-axis lattice constant? (>26 Å) Are there significantly larger lattice constants of the elements?
Figure 1.2 on page 12 of The Structure of Rare-earth Metal Surfaces linked below shows a repeating stack of hexagonal layers arranged as A B A B C B C A C... and several sources give the c-axis ...
- 5,720
0
votes
0
answers
41
views
Restoring potential of atoms in a solid
Above $\pu{0 K}$ the atoms in a solid are vibrating. However, what kind of potential restores each atom in the starting position?
Consider the crystal lattice of NaCl. The potential energy of a $\ce{...
- 193