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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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 do I index the spots/points in LEED patterns?

I'm trying to learn how to index the spots in LEED (Low-Energy Electron Diffractions) patterns and I have read some information regarding the subject but nothing seems to inform me regarding indexing. ...
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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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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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559 views

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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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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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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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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657 views

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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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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108 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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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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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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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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How to construct this spinel crystal structure?

I'm attempting to rebuild the crystal structure of γ-Al2O3 from calculated crystallographic data and am having some trouble. The primitive cell is repeated three times along the c-axis, leading to ...
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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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Reason behind more prioritising of normal spinels

According to my textbook: In normal spinels $\ce{A^{II}}$ should have occupied octahedral voids, but this factor is outweighed by greater lattice energy or smaller cation $\ce{B^{III}}$. Later, ...
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Unit cell structure of ionic crystal

I have a question about the structure of an LiH unit cell, and while this is related to a homework problem, it isn't the problem itself, I'm just looking for conceptual understanding. I've already ...
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Stacking two square (2D) layers to make a 3D close packed structure

My textbook states these ways of stacking 2D layers to make 3D close packed structures: Square close packing layer over Square close packing layer (though not written explicitly, the illustration ...
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XRD: Can stacking faults cause pseudo-centring?

Consider a cP lattice with a = 10 Å and an octahedron residing on each of the unit cell's vertices as shown below: The maximum symmetry will be Pm-3 m. Now, let's consider there are stacking defects ...
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Is the number of tetrahedral voids always equal to double the number of octahedral voids in any crystal?

I came accross the question whether the number of tetrahedal voids is always equal to twice the number of octahedral voids (in the case where both the voids are present). The key was given as the ...
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Melting point of crystalline solids

Why crystalline solids have sharp melting points but melting point of amorphous solids vary within a range? Is it because the interaction energy is equal between atoms of crystalline solids so they ...
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Why are crystalline solids anisotropic? [closed]

Why crystalline solids are anisotropic whereas amorphous solids are isotropic? Is it because in crystalline solids, X, Y and Z dimensions vary, but so does in amorphous. Please write as simple as ...
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Conception and manufacture of the Avogadro Project's (nearly) perfect silicon sphere (and, what is “atomic feeling”?)

The Avogadro Project, an effort prior to the recent redefinition of Avogadro's constant to design a nearly perfect sphere of silicon-28, apparently relied on the fine fingers of optician Achim ...
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Are clathrates and interstitial compounds the same thing?

In the book$\ce{^{[1]}}$, it's given that clathrates are compounds in which gases are entrapped within cavities of crystal lattices of certain organic or inorganic compounds. Interstitial compounds ...

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