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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.

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Why is the miller Index the way it is [on hold]

Why would one want to talk about directions and planes like that??? why not just give some basic description of it? why is it usefull to get the inverse of the numbers? Why are the Miller Index the ...
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What would superionic water ice look like?

Phys.org's Giant lasers crystallize water with shockwaves, revealing the atomic structure of superionic ice links to Nature Physics: Experimental evidence for superionic water ice using shock ...
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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 ...
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How can I get xyz coordinates of atoms of a unit cell structure from CIF format files?

I'm trying to run DFT or other 1st principle simulation of Pyrope ($\ce{Mg3Al2Si3O12)}$ and Grossular $\ce{(Ca3Al2[SiO4]3)}$ unit cell structure. So, I'm looking for unit cell xyz periodic box ...
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Difference in properties of water as ligand vs 'in lattice'

I'm trying to understand the difference in properties between water in crystals in different positions in the lattice. In this wikipedia article It quotes: Both notations can be combined as for ...
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What is the crystal structure of bismuth oxyhydroxyphosphate (BOHP)?

The recent Chemical & Engineering News article Photocatalyst shreds drinking water contaminant PFOA report the following: Cates and his colleagues made an accidental breakthrough while testing ...
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Possibility of non-hexagonal graphene

I understand that monolayer carbon naturally forms in a regular hexagonal tiling. Is it, however, possible (if difficult) to form carbon monolayers of a different structure? A 3-12-12 tiling, for ...
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187 views

Contribution of Tetrahedral and Octahedral voids in HCP

I cannot find anywhere what the contribution of atoms situated at octahedral or tetrahedral voids in a HCP unit cell would be. I need to know this to be able to calculate the formula of a compound ...
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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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Explain why body-centered tetragonal is a Bravais Lattice, but based-centered tetragonal is not?

Can you explain it using schematics? I think the reason is the symmetry that doesn't allowed to unique lattice points.
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charge transfer between layers of graphite with stacking fault

As a general rule, we only expect two parts of a system to have the exact same amount of charge if they are symmetry-related to each other. How much charge transfer would occur in graphite with a ...
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Why does alpha alumina have less surface area than gamma alumina?

Its been documented extensively that when gamma alumina (cubic) changes into alpha alumina (hexagonal) at temperatures around 1200 °C the specific surface area reduces considerably. What are exact ...
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Why does dielectric constant of crystal fluctuates in case of Frenkel defect in a crystal?

So I was studying Frenkel defect in crystal and came across this line that said The closeness of like charges tends to increase the dielectric constant of the crystal. I'm not able to understand ...
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Electrical resistivity [closed]

I have read that in non-metals solids the electric resistivity is reduced if we increase temperature.But this isn't logical.I mean if temperature is increased ok the electrons get extra energy but as ...
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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/...
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1answer
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Influence of the neighbouring molecules in a crystal at the example of XeF4

For reasons of symmetry I (without deeper chemical knowledge) supposed, that $\ce{XeF4}$ has a shape like $\ce{CH4}$. But according to Wikipedia its crystalline structure was determined by both NMR ...
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1answer
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What is the crystal structure of Calcium Acetate?

I tried conducting an experiment I saw at school with some materials I had at home. The experiment consisted of mixing a solution of Acetic Acid with Calcium Carbonate to yield Calcium Acetate: $$\ce{...
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Blue color in the blue persian salt [duplicate]

Blue persian salt has tiny blue framgents. So far I could found two explanations: It is sylvinite mineral inclusions As said in Wikipedia, "The intriguing blue colour occurs during the forming of ...
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3answers
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How do I know crystal structures from formula?

Give an explanation why $\ce{MgF2}$ and $\ce{CaF2}$ adopt different structure types. For example, the structure of calcium fluoride is 'fluorite' and the structure of magnesium fluoride is 'rutile'. ...
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Comparing the Lattice energy of different compounds

I am confused about some concepts related to Lattice energy. First of all,how to compare lattice energy between $2$ compounds belonging to different groups and periods? 1.Between $\ce{AlF3}$ and $\...
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1answer
67 views

Sodium Sulfate or Sodium Peroxysulfate? [closed]

In an attempt to clean drain cleaner, I reacted it with Sodium percarbonate to clean up some hardware store variety sulphuric acid. At first the reaction appeared successful, yielding a Nice Clear ...
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Gallium - Practical use to remove aluminium

Would gallium pass through aluminium into steel? The situation is two joined pieces of metal. Gallium could be applied to the aluminium to degrade it, for mechanical removal, but would it pass ...
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1answer
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Shape of urea molecule around N atom

I was doing a question where I was supposed to predict the shape of the urea molecule $[\ce{H2N(CO)NH2}]$ using Lewis and VSEPR. I identified that the N atoms will have a lone pair on them and so I ...
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1answer
158 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 ...
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1answer
137 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
338 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 ...
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1answer
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Why do noble metals like silver not form natural cubic crystals?

Pyrite forms cubic crystals, both in theory and in nature: However, the noble metals, like silver, that have cubic, face-centered lattices, do not seem to form cubic crystals in nature. One possible ...
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Directional emission from molecules

This might be a silly question (probably is). When a molecule absorbs it has a transition dipole moment, a measure of how strongly a certain transition will interact with light will depend on how ...
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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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2answers
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Understanding Equivalent Wyckoff positions

I'm somewhat confused by the concept of Wyckoff positions in crystal structures. From Quantum Chemistry of Solids by Robert Evarestov, the definition of a Wyckoff position is "all the crystallographic ...
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1answer
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Coordination number of spheres (all identical) in hexagonal close packing (HCP)

I was revising solid state chapter when I came across this question What is the maximum coordination number of an atom in a hcp crystal structure of an element? The word 'maximum' drew my ...
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2answers
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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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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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Are dopant ions on a crystal lattice free or bonded?

This question seems simple but I don't seem to find many answers right away for this. When you make a crystal doped with ions (like a luminescent phosphor) and the ions then become a defect in the ...
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1answer
102 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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2answers
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Lattice vectors calculation [closed]

How can I find the crystal lattice vectors, given the crystal parameters? For example, consider a crystal of rhombohedral symmetry, where a=b and c are known, and alpha=beta=90, gamma=120. How can the ...
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1answer
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What, if any, hydration states does sodium bicarbonate have?

Sodium carbonate has a few hydrates in addition to the anhydrous form. I haven't found any references online that assert any hydrates of sodium bicarbonate though. Do they simply not exist?
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The Conductivity of Electrolytes based on structure of Ionic Crystal [closed]

Background I want to run an experiment to test the conductivity of various ionic compounds dissolved in water. I was hoping to see some sort of trend in the increase/decrease of conductivity based ...
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2answers
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Formation of strontium peroxide

Wikipedia states: Strontium peroxide is produced by passing oxygen over heated strontium oxide. Upon heating in the absence of $\ce{O2}$, it degrades to $\ce{SrO}$ and $\ce{O2}$. I found some ...
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2answers
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Is there an equivalent unit cell that can describe a bcc unit cell where all points are the same element?

Similar to how an NaCl-structure can be described as just a primitive cubic structure if all the lattice points were the same element or ion. I'm asking if there any such alternative for the CsCl-...
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1answer
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Is this approach to finding density in crystal lattice acceptable?

In answering a question in an elementary chemistry text that asks for the density of gold ($\ce{Au}$) based on crystal dimensions and weight per atom, I found the approach I used was a little ...
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457 views

How thick is a snowflake?

The x, y dimensions of snowflakes get all the attention for obvious reasons, but the z dimension must be interesting too, in its own humble way. In fact, I have lived more than half a century and ...
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1answer
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The structure of sodium cuprous thiosulphate

While studying about copper sulphate, I came across a reaction involving sodium thiosulphate (Hypo) and copper sulphate. Although I don't know the utility of this reaction, I felt that it was ...
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1answer
299 views

How to calculate mass of water of crystallisation?

How do you work out the mass of water of crystallisation for 13.5 g of $$\ce{Al2(SO4)3*6H2O}$$ The correct answer is 3.24 g of water but I'm unable to derive the answer. What I have tried: I ...
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388 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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2answers
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Counting body centre as lattice point when the basis consists of 2 atoms

An article in my book gives the following informatiom :- I understood part a) and b) but faced problems with c). It says that here the basis consists of 2 atoms which doesnt seem to be very ...
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1answer
371 views

What do the six polymorphs of chocolate look like?

Today I learnt that chocolate tempering works by controlling the temperature to ensure the crystals set to one (type V) of the six polymorphs. What do these polymorphs actually look like? By that I ...
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1answer
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Polyhedron with four capping ions

Let's say I have a trigonal prism in my crystal structure and this is further capped by two ions it's called a bicapped trigonal prism. If I have three ions it's called a tricapped trigonal prism. But ...
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1answer
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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 ...
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How sure can we be about the structure of purine?

While answering the question Basicities of nitrogen atoms in purine, I noticed, that there might be a rapid interchange of the hydrogen bonded to the nitrogen atoms. I have found a crystal structure ...