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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 a rhombohedron considered the primitive unit cell for a hexagonal crystal system? [on hold]

I feel like the hexagonal Bravais lattices shouldn't include the rhombohedron as a subset of the hexagonal group. It isn't a hexagon, and no other Bravais lattice is rotated and translated to make the ...
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Sodium Sulfate or Sodium Peroxysulfate? [closed]

I needed some unadulterated H2SO4 to react with some steel wool to render Ferrous Sulphate then to ferrous hydroxide for some experiments with ferromagnetic cores. I thought to use Sodium ...
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21 views

Why the Pmcm group space is replaced by Pmma?

I had an exercice with a "Pmcm" cristal structure, I tried to do it and it was incoherent. I realized that this space group doesn't really exist : we need to change the base vector to have a Pmma ...
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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
73 views

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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What it the point group of bilayer MoS2?

When I see the structure of bilayer MoS2, its point group is 6/mmm by Materials Project. https://materialsproject.org/materials/mp-1018809/# Yon can download and see the structure from cif file. Can ...
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35 views

How to get ionic radii for coordination number = 12?

I am studying ABX3 perovskites, and I would like to calculate Goldschmidt tolerance factors for them. The A sites in these materials have a coordination number = 12. The Shennon's paper (R. D. ...
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43 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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Why does gallium have a low melting point (29 degrees Celsius)?

Gallium has the electronic configuration of [Ar]3d(10)4s(2)4p(1). So it can share the 4p electron with another Ga atom and exist as Ga(2), and so according to my intuition (as in case of Au and Hg, Au ...
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47 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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Efficient ways to make perovskite solar cell crystals

I'm a high schooler involved in a research in which we aim to grow perovskite crystals in microgravity. I've recently come across this article in which they explain how to grow better perovskite ...
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1answer
50 views

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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2answers
41 views

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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46 views

Types of unit cells of solid state

$\ce{NaCl}$ forms FCC unit cell but not BCC though $\ce{Na}$ atoms occupy body centre as well as edge centre. Why?
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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
117 views

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
82 views

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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1answer
33 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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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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38 views

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
59 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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361 views

Solid State — Locating and counting the number of voids in hcp structure

First off, a small doubt: Is the hcp structure same as the hexagonal crystal lattice (one of the 14 Bravais lattices)? Secondly, what is the unit cell of a hexagonal crystal structure based on the ...
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53 views

How to find out which plane in a cubic structure has the highest density?

For a cubic structure (namely FCC, BCC, or simple cubic) we can always draw a plane and predict the plane which has highest density of atoms. Is there any rule of thumb to arrive at such a plane? How ...
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2answers
74 views

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
76 views

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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Incomplete definition of the unit cell of a lattice

All of the books/online sources that I have found cite the following definition of the unit cell of a lattice : The unit cell is defined as the smallest repeating unit having the full symmetry of ...
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1answer
35 views

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
86 views

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
53 views

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
41 views

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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253 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
251 views

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
61 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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199 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
92 views

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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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? Also, what ...
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1answer
31 views

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
42 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 ...
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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 ...
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1answer
678 views

How to determine the edge length of the aluminium unit cell?

I'm having trouble understanding why I can't get the correct answer from this homework problem: Solid aluminum forms a face-centered cubic unit cell. Aluminum has a density of $\pu{2.70 g/cm^3}$. ...
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182 views

Structure of Dolomite [closed]

This the structure of Dolomite. Can someone explain this structure to me?( like what are the blue, yellow etc atoms are? why are they arranged this way?) Any help would be appreciated.
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187 views

Simple/ Primitive Tetragonal Bravais Lattice [closed]

Are there any elements which exhibit the Simple(Primitive) Tetragonal Bravais Lattice?
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1answer
42 views

What is the modern hardware/supermarket term for 'laundry bluing'?

I want to make this amazing paper Crystal Tree with my kids. One of the ingredients is laundry bluing. It is described thus: The magic crystals that are left behind are a combination of the Mrs. ...
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2answers
124 views

Ice Crystal Matrix measurements of H2O molecules?

I want a mathematically generated 3D STL copy of this image, however it's represent algorithmically. If I do all the H2O's as individual pieces with female connections prepared for chopped bike ...
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714 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 ...
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1answer
46 views

How dried up detergent water led to precipitation of snowflake like shapes?

I forgot to drain the water off the bucket (after cleaning stain from a piece of clothing with detergent) and left it for few days. After few days when I needed it back, I found these glittery very ...
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1answer
36 views

Greater bond distance for silicon diamond structure than for carbon diamond structure?

In the silicon diamond structure the bond distance is about two times the bond distance of the carbon diamond structure. Is this caused only by the greater dimension of $\mathrm{Si}$ atoms with ...
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403 views

Image of crystal structure

Is there any websites or resources where I can get a good image of a certain crystal structure? In my case I'm looking for lead(II) tungstate $\ce{PbWO4}$ and I can't find a vivid graphic on google (...
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Radius of iridium atom from crystallographic data [duplicate]

Calculate the radius of iridium atom, given that $\ce{Ir}$ has an FCC crystal structure, a density of $\pu{22.4 g cm-3}$ and atomic weight of $\pu{192.2 g mol-1}$. My solution: Why does it seem ...
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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 ...