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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On the exact definitions of Frenkel and Schottky defects

The wiki page on vacancy defects says; It is also known as a Schottky defect, although in ionic crystals the concepts are not identical. As far as I'm aware, they're the same. Furthermore, the wiki ...
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Determination of timescales using characterization methods

There are 4 different timescales in material characterization (as classified in the Atkins textbook): a. Time during which a quantum of radiation or a particle can interact with a molecule. b. ...
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What is the crystal structure of ammonium hydrogen sulfate? It's beautifully birefringent

I make art using a microscope and camera. I have heated ammonium sulphate that decomposes to ammonium hydrogen sulfate, melts, and then recrystalises to produce exceptionally beautiful birefiringent ...
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How much heat is required to dehydrate a hydrate?

If I have a hydrate, such as copper (II) sulfate pentahydrate, $\ce{CuSO_4 \cdot 5H_2O}$, what is the amount of heat to required to dehydrate it? I assume that it is equal to or greater than the ...
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What is the maximum number of water molecules that has been recorded till date to present as water of crystallization in a compound?

Context: I was casually looking through some old questions when I found this question. The OP wanted a compound that has all the hydrates ranging from monohydrate to decahydrate. I found chromium(III) ...
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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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Why is the disordered CuAu structure more stable at high temperatures?

I know that the disordered CuAu structure is based around FCC whereas the ordered CuAu structure is tetragonal. Why would the FCC structure be more stable at high temperatures? For context, I was ...
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Struvite Crystals: How does it form?

I'm in general chemistry, and I was wondering how ionic species crystallize and form the shapes they do, specifically in regard to the Struvite precipitate $\ce{MgNH_4PO_4. 6H_2O}$. Deconstructing the ...
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Converting fractional coordinates into cartesian coordinates for crystallography

So let's say for a given molecule I have the volume of a unit cell, the shape of the unit cell (monoclinic, cubic, etc), the cell angles alpha, beta, and gamma, the cell lengths a,b, and c, and a list ...
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Why Frenkel defect does not impact the density of the solid?

The following text is from Chemistry Part I - Textbook for Class XII (NCERT), chapter "The Solid State", page 23, topic "1.9 Imperfections in Solids", sub topic "1.9.1 Types ...
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Height of CCP Lattice

Are the height of the Cubic Close packing Lattice and the cubic Hexagonal Close Packing the same? My understanding says that these unit cells are formed by different arrangement of atoms, ABC for CCP ...
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$P 4_{2} 22$ tetragonal group choice of origin for symmetry of special projections

I was looking at the description of the tetragonal group $$P 4_{2} 2 2$$ (No 93 in the International Tables of Crystallography) and there is one aspect that I do not understand. Namely, what is the ...
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Find the Linear Packing factor of FCC [-1 -2 1]

I have been trying to figure out this question, and essentially if I assume that the only atoms that the vector touches are the starting and ending atoms, then I get 0.58. I am trying to find a more ...
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octahedral interstitial sites located entirely within a full hexagonal HCP unit cell at a height of $c/4$ up from the bottom of the unit cell

I have been trying to visualize and find the number of them for a while, through the image attached. I can't tell whether the c/4 part includes the octahedral site or not...how should I go about ...
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Miller Indices of Goldnanoparticles from Turkevich and Frens method

I need the miller indices of gold nanoparticles that were synthesized after the route of Turkevich and Frens. I during my research I found a lot of publications, but it looks like no one measured it ...
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How to create .CIF file from DRX data in a paper, for compound not found in crystallographic database

I tried to recover a .CIF file with the crystal structure for the compound discussed in this 2006 paper, strontium hydroxide octahydrate - $\ce{Sr(OH)2·8H2O}$ - from Cambridge Crystallographic Data ...
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Interatomic spacing vs electric conductivity

I have a theory which may be wrong but I will write it down.If 2 elements at the same group (in solids)have the same crystal structure then the one with the biggest interatomic spacing has better ...
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Why is the ionic radius of hydride so large?

The order of ionic radii for halides and hydride is apparently as follows: $$\ce{F-} < \ce{Cl-} < \ce{Br-} < \ce{H-} < \ce{I-}$$ Why is the hydride ion so large, even larger than bromide ...
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What would oxygen or nitrogen snow look like?

I was watching a video of what would happen if the earth got kicked out of the solar system and at one point it was mentioned that oxygen and nitrogen snow would form. So would such snow be any ...
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Extracting “Crystal Radii” from a CIF file

I'm currently downloading .cif files from various online databases and using openbabel to convert the fractional coordinates that are in the .cif files into .xyz files. The typical output will look ...
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Change of ionic packing upon crystals are pressurized

When rock salt crystal is pressurized, its FCC structure changes to BCC structure whereby coordination ratio changes from 6:6 to 8:8. At the same time packing efficiency of the crystal decreases from ...
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How does VB theory explain the Si-O-Si bond angles in SiO2?

Silicon dioxide has a huge variety of structures. Most of them are built up from connected $\ce{SiO4}$ units — the $\ce{O–Si–O}$ angle is $109.5°$, accordingly. The VB/hybridization approach to this ...
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Sketching lattice points, primitive axes, primitive cell, and basis of atoms

I am currently studying Introduction to Solid State Physics, 8th edition, by Kittel. Chapter 1 provides the following figure and accompanying explanations: It also says the following: An ideal ...
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How to find the atomic packing factor of Sodium Chloride (and other FCC ionic compounds in general)?

For a piece of coursework I am doing, I need to calculate the atomic packing factor of some ionic compounds. I have had no formal teaching in this area, so what I know comes from information I have ...
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How is ECR (Electron Counting Rule) done in a structure?

I've been told how to apply the ECR to GaAs{001}(2×4) in my lectures but it makes no sense to me and I don't seem to be able to find any other sources that explain this. (This is a further question on ...
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An automated approach to visualize several xyz structures

I have several .xyz files (each composed of several molecules) and I'd like to find an automated way to visualize and save them. I'd appreciate any guidance.
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Are diamonds as chemically inert as glass? [closed]

Every beaker that I have seen in a lab is made of glass. Glass, as I understand, is made of SiO2, or silicon dioxide, which has a crystalline structure that is similar to diamond. This property causes ...
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What are Lattice Points?

What are lattice points exactly? For what purpose are they used in solid state chemistry?
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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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Is the lattice point in ZnO crystal structure occupied by the molecule ZnO or the ion O^2-/Zn^2+?

I learnt that ZnO has a hexagonal crystal system. I was expecting that cations or anions would occupy the lattice points in hcp while voids would be occupied by anions or cations respectively. But ...
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Bravais Crystal Lattices and Voids

What is the difference between Hexagonal Close Packing (HCP) structures and the hexagonal crystal Bravais lattice? I've looked up some sites but can't seem to understand them. It would help if you ...
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What is meant by “basis” in “… its basis in particles leads to a material comprising crystallites or grains tightly bound together, …”?

I am currently studying Ultrasonic transducers – Materials and design for sensors, actuators and medical applications by Kentaro Nakamura. In chapter 1.2.1 Ferroelectricity, the author says the ...
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Can a crystal structure of a substance appear or disappear?

I read somewhere before that some substances no longer crystallize naturally in some specific structures, although it do that readily before. Instead, new structures that never happen before become ...
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Why is Cubic closed packing called “cubic”?

How is Cubic Closed Packing "cubic" and also how is hexagonal closed packing "hexagonal"? I have been thinking over this for a few hours but I am unable to visualise. I understand ...
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If a good choice of a unit cell should be the one of most symmetry ,then why keep body centered tetragonal if face centered cubic exists?

For any lattice a good choice of a unit cell is the one that is the most symmetric. Now if every lattice made by a body centered tetragonal unit cell can be made by a face centered cubic unit cell ,...
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Conventional unit cell for a hexagonal crystal system

The figure shows a unit cell of a hexagonal crystal system. Drawn in bold, is the unit cell. The lightly shaded one is a unit cell as well and has a six fold symmetry along an axis, hence is more ...
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Interplanar distance given Miller indice of the planes

Say we've a cubic crystal of unity edge length. A set of planes in such a crystal is specified by their miller indice as $(3 2 0)$. One of these planes then has intercepts on the axes as $(2 ,3 ,\...
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Trouble understanding interplanar spacing using miller indices

We know that two parallel planes have the same Miller indices, this implies that we can have an infinite number of parallel planes close to one another all of which have the same Miller indices. But ...
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How to differentiate hydrous and anhydrous compound? [closed]

For an experiment, my teacher gave me containers of hydrates and their corresponding anhydrous compounds, but I have a feeling that for one of the compounds she switched the hydrate and anhydrous ...
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If stirring negatively affects crystal purity, why is it so?

My Intellectual Expectations Intuitively, I would expect strong stirring to improve crystal purity during the process of crystalization. My rationale is that strong stirring would increase contact ...
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Is iron(iii) hydroxide equivalent to hydrated iron(iii) oxide? [duplicate]

Are the chemicals $\ce{Fe(OH)3}$ and $\ce{Fe2O3⋅3H2O}$ equivalent? They are both network solids and have the same empirical formula but I know that doesn't always mean they are structurally the same.
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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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Why are so many ionic compounds brittle?

Even when ionic compounds are strong (e.g. rubies and sapphires), they are neither malleable nor ductile in the slightest, and if sufficient stress is put on them, they will shatter, not bend. Why is ...
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Having trouble understanding the iron-carbon phase diagram

At room temperature, alpha and alpha+$\ce{Fe3C}$ are present (depending on carbon content), which is ferrite and pearlite. In the lab we polished and etched samples of carbon steel to observe the ...
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Why is SiO2 a solid while CO2 is a gas?

I was under the impression that chemistry almost exclusively involves valence electrons because there isn't enough energy to strip off electrons located closer to the nucleus. If that is true, and ...
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What is the reason for isotropy in amorphous solids?

In my book, it's been mentioned that crystalline solids are anisotropic whereas amorphous solids are isotropic in nature. The reason for these has been explained (with a diagram) as: Crystalline ...
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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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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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How do I find miller indices for a plane whose intercepts are fractions of the lattice constant?

[I'm talking with respect to cubic lattices alone.] For instance, if a plane has $x,y,z$ intercepts $a/2,a/2,a/2$ (where $a$ is the lattice constant) the miller index would be $[2\space2\space2]$. The ...
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Hydrogen bonding in sugar acids

I recently learnt that the reason for low solubility of mucic acid as compared to glucaric acid was more hydrogen bonding in the crystal state of mucic acid as compared to glucaric acid. I would ...

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