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 upon melting of PEO between crossed polars colours appear?

Crystalline PEO when under crossed polars shows distinct Maltese cross pattern. Being birefringent, when polymer crystal align with the polarizer or analyser it shows extinction regions (effect known ...
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What type of solid is BeCl2? [closed]

My textbook says that $\ce{BeCl2}$ is a molecular solid. However, the Wikipedia page states that $\ce{BeCl2}$ polymerizes in the solid state because $\ce{Be}$ is electron deficient. Does this mean ...
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What do X-ray diffraction and NMR tell about the Proteins? [closed]

I have gone through a simple idea that proteins have different conformations; it is a dynamic system. Moreover, whenever we do ensemble experiments, so we get an average picture. There are some ...
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When H2NCH2CH2PH2 acts a monodentate ligand, it is the phosphine end that chelates. Why is that?

In some occasions, if the ligand acts on Pd it do so as a monodentate ligand. I am attempting to explain this phenomenon but came into a block.
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Why the atomic (metallic) radius of gallium is less than that of aluminium?

It is a well known fact that on moving down the group of p-block elements, the atomic radius is expected to increase. However, gallium is an exception. The atomic radius i.e., the metallic radius of ...
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What is a material more easily cut than shattered? [closed]

I'm currently developing a sci-fi concept for animation which partially involves a typical "the earth has been overrun by XYZ" scenario. One of the ideas for XYZ we're thinking of is a species of ...
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Crystal structures of heaviest nuclides' compounds

What is the heaviest element of the periodic table for which there is a compound whose crystal structure has been completely resolved by X-ray diffraction?
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Unexpected result (sodium hypochlorite & steel wool)

So I got myself a large Erlenmeyer flask, some steel wool and the bleach from the bathroom, mixing them under safe conditions in small quantities to see the sparky reaction I'd heard about. Trouble is,...
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Does crystalline glass exist?

As far as I know, glass is a non-crystalline amorphous solid. Does glass exist in crystalline forms? Or is it the definition of glass that it's non-crystalline, in which case my question is based off ...
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If the appearance of a crystal is octahedral crystals, can I deduce that the crystal structure is octahedral?

I have a physics problem in which I'm calculating the magnetic properties of "a paramagnetic salt like iron ammonium alum". I am half inclined to believe that I am supposed to treat the substance ...
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How to control nucleation of NaCl crystals?

In addition to a previous question I posted, I have a second question. The previous question I shall link here: How to counter crust formation when crystallizing NaCl on the liquid-air interface? ...
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How to counter crust formation when crystallizing NaCl on the liquid-air interface?

Saturated sodium chloride solutions are evaporated at elevated temperature. The aim of evaporation is to produce hollow pyramid salt crystals. Temperatures used range from 65°C to 85°C. With 80°C ...
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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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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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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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How does VB theory explain the bond angles in SiO2?

Silicon dioxide has a huge variety of structures. Most of them have a tetrahedral $\ce{SiO2}$ unit cell — the $\ce{O–Si–O}$ angle is $109.5°$, accordingly. The VB/hybridization approach to this ...
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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 to calculate the height of an hcp lattice?

A hexagonal closed packing (hcp) unit cell has an ABAB type of packing. For calculating the packing fraction we require the volume of the unit cell. Volume of hcp lattice = (Base area) $\cdot$ (...
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Crystal structure of solid (frozen) hydrogen fluoride?

Wikipedia says the HF molecules form zig-zags, but doesn't mention any larger-scale organization. Is it amorphous, similar to glass? (https://en.wikipedia.org/wiki/Hydrogen_fluoride)
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How to formally calculate the surface density of layered materials such as graphene?

Typically density is defined in units of mass per volume. In the case of graphene it is mass per area, i.e. surface density. What would be the correct way to calculate the surface density (mass per ...
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Does bicarbonation require water?

In an aqueous solution of $\ce{NaOH}$ exposed to the atmosphere one can probably expect some degree of $$\ce{NaOH(aq) + CO2(g) -> NaHCO3 (aq)}$$ But, what would happen if just a solid block of $\...
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Growing crystals that are in a magnetic field or subjected to an electric field

I know different crystals resonant at different frequencies but is it possible to grow crystal at a certain frequency. An example would be growing crystals using Epsom salt or Alum in a magnetic ...
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Why are there only 7 types of unit cells and 14 types of Bravais lattices?

Why are there only 7 types of unit cells and 14 types of Bravais lattices? I was reading about solid-state chemistry for the first time and this limitation made no sense to me. I tried to do the ...
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Symmetry Space Group Diagram

I am doing an introductory course to Crystallography and I have found in the following web page: http://pd.chem.ucl.ac.uk/pdnn/symm3/sgmonoc.htm a guide for the elaboration of the diagrams of the ...
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Ce₂(SO₄)₃ solubility in water [duplicate]

I have mostly come across examples of solids whose solubility increases in liquids with an increase in temperature. However, there seem to be exceptions to generalized rule this such as the solubility ...
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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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Is diamond an allotrope or polymorph of carbon?

Is diamond an allotrope or polymorph of carbon? When is something considered an allotrope vs a polymorph?
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Crystallographic terminology associated with the honeycomb structure

I'm trying to quickly learn basic crystallographic principles in 2D under pressure (it's me whose under pressure, not the lattice) so I'm checking many sources to find those that "speak to me" the ...
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Are there examples of crystals with random but static mixtures of two unit cell configurations?

The image in this question turned out to probably be wrong, but it still makes me wonder. Are there examples of crystals where the atoms within a unit cell can have two (or more) different ...
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Determining structure factors for crystals from lattice and motif

I understand that the structure factor for a crystal is given by: $$F_{hkl} = \sum_r f_{r} e^{2{\pi}i(hx_{r}+ky_{r}+lz_{r})} $$ My textbook (''Structures of crystals'', Glazier) suggests that you ...
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Calculating distance between adjacent planes (hkl) in a simple cubic crystal

My textbook says the following in a section on Miller indices: Adjacent planes $(hkl)$ in a simple cubic crystal are spaced a distance $d_{hkl}$ from each other, with $d_{hkl}$ given by: $$d_{...
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Question about Elemental Sulfur

I am trying to understand the structure of elemental, crystalline sulfur. I read that it is face-centered orthorhombic. My question is whether each point on the unit lattice contains a single atom of ...
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Which theta should be taken from x-ray diffraction pattern for calculating Scherrer's equation?

We use Scherrer's equation to calculate crystalline size of a particle: $$d = \frac{Bλ}{β\cos{θ}}$$ But which theta should we take from the XRD pattern for this calculation? For example, the ...
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Miller indices: How does one translates the orientation to the origin of the unit cell?

In a section discussing Miller indices, my textbook says the following: The rules for determining the Miller indices of a direction or an orientation in a crystal are as follows: translate 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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Understanding lattice matching of graphene on silver (111) crystal surface and meaning of the √3 x √3 lattice?

Figure 1 in Ivor Lončarić and Vito Despoja, Phys. Rev. B 90, 075414 Benchmarking van der Waals functionals with noncontact RPA calculations on graphene-Ag(111) (available in Researchgate) shows a ...
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How can I find the smaller symmetric structure from big crystal unit cell?

I have Pyrope (Mg3Al2(SiO4)3) crystal structure, downloaded from materialsproject: https://materialsproject.org/materials/mp-6073/# It appeared as triclinic cell, but if you download CIF file and ...
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A unit cell for graphene

In a study I have run into some questions asking for "How many atoms are contained in the unit cell" for graphene. I have some trouble understanding the unit cell of graphene which is always depicted ...
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Why doesn't beryllium, an elemental solid, obey Dulong and Petit's law?

Beryllium has a molar heat capacity of $\pu{17.7 J mol-1 K-1},$ which is quite far from the $\pu{25 J mol-1 K-1}$ as predicted by Dulong and Petit's law. What is the reason for this discrepancy?
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Why is Polonium the only metal to crystallize forming Simple Cubic Cell?

I have read that Polonium is the only metal that crystallizes forming SCC. I searched for a concrete explanation but all they were saying is the stability of Polonium at STP. I can't really comprehend ...
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Why does pyrite form cubic crystals?

Pyrite ($\ce{FeS2}$) forms cubic crystals, like these ones: I know that the crystal structure is primitive cubic, but I don’t see how cubic structure on the molecular level translates to cubic ...
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Why is Libethenite (Cu2(OH)PO4) color green?

It is not a complex compound and the copper atom is not oxidized so I'm wondering how does its color change. The book mentioned that at favorable conditions, adding water in Copper phosphate, which is ...
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Why don't ionic compounds show stereoisomerism?

When I was reading about crystalline nature of ionic compounds, I came across the statement that ionic compound doesn't show stereoisomerism. What does that mean and can anybody explain the reason ...
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Silver (111) surface structure, and is bulk structure body-center or face-center cubic?

I'd like to understand the atomic arrangement is on a silver (111) surface. Step 1 would be to find out the bulk crystal structure. Wikipedia lists silver as face-center cubic (fcc) here and here ...
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Effect of dopant size on XRD peak shift

If we add an impurity atom (doping) to the crystalline struture of another material and take the XRD of the doped material what kind of peak shift can we expect. For the better description of my ...
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Replacement for optical calcite (Glan Thompson prism)?

I notice that Glan Thompson prisms seem to be the preferred optics for doing polarimetry and have been for at least 75 years. One instrument maker says that polaroid films can be used but they tend to ...
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Lattice energy while bond formation [closed]

My chemistry lecturer taught us that lattice energy is the energy required to break an ionic bond between two oppositely charged ions in a crystal lattice. He then told us that lattice energy is ...
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Could you form quartz crystals by melting and cooling sand very slowly?

Since glass is amorphous quartz and when you slow the cooling of something enough it will crystallize, couldn’t you melt $\ce{SiO2}$ (sand) and then very slowly cool it to cause spontaneous nucleation ...
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Is (high) pressure required to form (quartz) crystals?

I've been reading a lot of sources about the hydrothermal synthesis of quartz using autoclaves. I want to try doing this myself, but before I can I need to know the minimum pressure required. If you ...
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Physical meaning of thermal parameters dimension (Ų)

In single-crystal x-ray crystallography both isotropic and anisotropic displacement parameters $U_{ij}$ of thermal ellipsoids have dimension of square angstrom ($Å^2$) as follows from the definition ...