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 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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201 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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933 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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176 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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623 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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440 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 on ...
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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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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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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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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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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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680 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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359 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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710 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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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
112 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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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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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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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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1answer
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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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70 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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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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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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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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107 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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341 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 $\...
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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 ...
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Why shape of diamond is like diamond?

I know that in diamond carbon atoms occur in 3d geometry but i want to ask that why it is in shape of diamond not like some other 3d geometrical shape like cube or cuboid?
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What is the Difference between Menthol Crystal and Menthol Powder?

I want to buy menthol powder from a chemical supplier but he is selling menthol crystal at half price of menthol powder (he says manufacturing process is the difference) so I am really confused what ...
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How can you inhibit crystallisation of hot superconcentrated magnesium sulphate [closed]

I’m trying to create a gel like solution of primarily magnesium sulphate heptahydrate or Epsom salt and water. It’s simple to create a hot super concentrated solution but when it cools it’s obviously ...
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Formula of the compound based on occupancy of lattice voids

Atom of element $\ce{B}$ forms HCP lattice and those of the element $\ce{A}$ occupy 2/3rd of tetrahedral voids. What is the formula of the compound formed by the elements $\ce{A}$ and $\ce{B}$? My ...
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Can you heat Bismuth crystals to reset the oxide layer for new colors?

I'd like to get a bismuth crystal with small structures and deep blue colors for a ring I want to make. I can find these properties in different crystals online but never together. Can I just take a ...
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What is the crystal structure for a crystal where the ratio of the squares of the angle peaks is 0.825?

I followed this and it gives an example of how to identify a crystal structure using XRD data. I have an unknown alkali halide where two peaks were found at $2\theta =25.66$ and $2\theta = 28.3$. I ...
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What can be concluded from two different values for the interplanar distance between planes of atoms in an X-Ray diffraction experiment?

I analyzed an unknown Alkali Halide crystal using x-rays from a copper source. I need to find the d-spacing for this crystal, i.e. the interplanar distance between planes of atoms. I found my $K_\...
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How do I calculate lattice points per unit volume? [duplicate]

My professor was explaining simple cubic, body centered cubic, and face centered cubic lattices and I didn't quite understand the calculations below: Simple Cubic: $8 \cdot 1/8 = 1$ lattice point per ...

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