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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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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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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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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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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$P 4_{2} 22$ 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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23 views

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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1answer
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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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51 views

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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35 views

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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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 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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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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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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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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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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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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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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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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57 views

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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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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355 views

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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1answer
58 views

Database of 3D crystal models [closed]

I'm looking for a database of very basic crystal models for all the various types - triclinic, monoclinic, orthorhombic, tetragonal, rhombohedral, hexagonal, and cubic. A basic example would be a CAD ...
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Finding Equivalent representation of a molecule/crystal

Is there a website or online calculator to determine the reducible representation of a crystal/molecule using wyckoff positions without having to analyse the number of unmoved atoms/bonds for ...
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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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How to find bond lengths from .cif files of crystal structure

I am confused about how to calculate the bond lengths within a given structure given its .cif file. I have highlighted the bond of interest in the image below. The atom coordinates are shown in the ...
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If I break a crystal, would the “broken” pieces also have the same crystal shape? [closed]

If I've a crystal of some particular geometrical shape and i hammer it and it breaks into small pieces. Will the small pieces have the same shape as of the parent crystal?
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What is meant by “rotation about an axis that passes through a lattice point”?

I am currently studying Introduction to Solid State Physics, 8th edition, by Charles Kittel. In the section Fundamental Types of Lattices of chapter 1, the author says the following: Crystal lattices ...
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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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1answer
37 views

Microscopic image [closed]

When I was reading a chapter on solids structure then i thought of how the real structure would be like if seen from microscope. Hence I want the real microscopic molecular image of NaCl(common salt) ...
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How is the Born-Lande equation modified when the structure is not NaCl?

Often the Born-Lande equation is quoted (alongwith the calculation of the Madelung constant and Born exponent) with reference to rock-salt structure. But what if we take some other crystal, like ...
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Is LiNbO3 a perovskite or not?

I am collecting a database of perovskite materials and could not decide if $\ce{LiNbO3}$ is categorized as perovskite or not. $\ce{LiNbO3}$ has been identified as a perovskite [1] as well as non-...
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How many nearest neighbours does a corner atom have? [closed]

Figure shows a unit cell of a cubic lattice. The atom in the middle has 8 nearest neighbours (the atoms in the corner). How many nearest neighbours does a corner atom has ? I identified the given ...
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Determining cation-to-anion radius ratio for “ideal” Anti-fluorite structure

My book under the heading of Anti-fluorite structure makes the following remark, about the radius ratio of an ideal Anti-fluorite: The ideal antifluorite would have a cation-to-anion radius ratio ...
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156 views

How to identify if a material is perovskite or not?

This is more of a materials science question, but I believe many of you have referred NIST Inorganic Crystal Structure Database (ICSD) database. I am collecting a database of perovskite materials and ...
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190 views

Are HCP and Primitive Hexagonal Unit Cell the same thing? [closed]

In HCP, the [2D] Hexagonal packed layers are arranged in ABAB form. The same happens in Primitive Hexagonal Unit Cell. So does that mean they are the same? If not what differentiates one from the ...
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Why rutile structure have primitive unit cell instead of body centered?

In the literature (Wikipedia), I read that $\ce{MgH2}$ have a structure of rutile. Then, I looked at its space group which is $P4_2/mnm$. From this notation, I understood that it possesses a (...
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1answer
324 views

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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Bonding and coordination of oxygen in a Ga2O3 crystal structure [duplicate]

I'm trying to find the crystal structure of gallium oxide ($\ce{Ga2O3}$). However, I find the images of the crystal structure in the peer-reviewed journals problematic. First, I hop to the wikipedia ...
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1answer
106 views

Origin in a crystal

I am trying to understand the International Tables for Crystallography. How can I identify the origin in the image on the left? Without knowing the origin, I cannot identify the position of the ...
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Does a [B4O8]4- anion really exist?

I am currently collecting information for an abstract and therefore I wanted to discuss different $\ce{[BO3]^3-}$ and $\ce{[BO4]^5-}$ connectivities. I also found a book on crystallography and the ...
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Chemical bonding and crystal structure of silicon [duplicate]

I can understand that in Silicon Crystal a central Silicon atom shares its 4 valance electrons with 4 surrounding silicon atoms. And the chain continues. But then What happens to the outermost such ...
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How to Visualize the crystal planes of calcite?

I've been struggling to visualize the structure of calcite. Most papers say it grows in a rhombohedron capped by (104) faces. However, I don't see why it would do this when looking at it using ...

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