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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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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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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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684 views

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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105 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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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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283 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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430 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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963 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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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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121 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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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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676 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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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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156 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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479 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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366 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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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
183 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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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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801 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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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
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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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606 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
315 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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1answer
580 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
95 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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135 views

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
4k 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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533 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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352 views

Simple/ Primitive Tetragonal Bravais Lattice [closed]

Are there any elements which exhibit the Simple(Primitive) Tetragonal Bravais Lattice?
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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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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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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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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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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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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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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 ...
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222 views

How to visualize a crystal from a unit cell PDB and how to draw the unit cell's axes? [closed]

I am looking at the following PDB experimental data: Length (Å) Angle (°) a = 155.72 α = 90.00 b = 155.72 β = 90.00 c = 106.16 γ = 120.00 I find it hard to ...
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Can I supercool and solidify a liquid multiple times?

Let's say that I supercool a bottle of beer and then tap it so it freezes and solidifies. If I were to allow the frozen beer to melt completely, and then freeze the same bottle again, would it still ...
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1answer
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Local resolution of a crystal structure in PDB File (protein data bank)

I am wondering if it is possible to find the local resolution of a crystal structure. Usually, the resolution of the PDB is assigned the resolution of the highest resolved part of the protein/nucleic ...
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Sense of radii quotient to determine coordination number in crystals?

Every common textbook explains the method of the radii quotient between the cation and anion of a selected salt to determine to coordination number(s) in that salt. For example deduce "Inorganic ...
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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 ...
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101 views

Generating PDB file from electron density without force field minimization

Is there a step-by-step tutorial on how to generate a PDB file from an electron density file (*.ccp4)? For my current project, I am trying to take some statistics ...
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326 views

Metallic Bonding

Since in metallic bonding, metals form ions and are surrounded by delocalized electrons, does that mean metal atoms always react in this ionised state? Can metal atoms lose valence electrons (like $\...