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 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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Calculating nearest neighbor distances

For cubic materials, there are equations in which to calculate nearest neighbor (NN), second nearest neighbor, etc. Can this be done with tetragonal crystal structures? I want to calculate NN, 2NN, ...
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Identifying a Positive or Neutral Ligand Inside Coordination Sphere?

There are some coordination compounds like $\ce{Na2[Fe(CN)5NO]}$, where ligands like $\ce{NO}$ are used which exist as both $\ce{NO+}$ (nitrosonium ion) and $\ce{NO^.}$ (neutral nitrosyl). How to ...
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To what extent are the radius ratio rules valid for predicting the crystal structure of an ionic compound?

The ionic radii of $\ce{Ba^2+}$ and $\ce{O^2-}$ in barium oxide are $\pu{135pm}$ and $\pu{140pm}$, respectively. The ratio of the radius of $\ce{Ba^2+}$ to $\ce{O^2-}$ is approximately $0.964$. ...
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Finding $c$ with Dulong-Petit law on non-molecular substance

The Wikipedia article states the Dulong-Petit law as follows: $$c=\frac{3R}M$$ $c$ is specific heat capacity $[\mathrm{\frac J{kg\; K}}]$ and $R$ the gas constant. $M$ is the molar mass in [g/mole], ...
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Why we don't talk about unit cells in hcp/fcc structures?

I'm studying basics of Solid State Chemistry from this source. So there are 14 types of Bravais crystal lattices (Primitive + Centered) in 3D. Every solid in this universe is made by the unit cells ...
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Miller Indices: How to deal with some weird(-ish) cases?

I've recently been doing a spot of self-learning (Crystallography), and some of the examples provided in the Wikipedia article for Miller Indices have stumped me. I can't for the world figure out how ...
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Calculating the theoretical Density of a Lithium oxide

I am trying to calculate the theoretical density for lithium oxide using the following formula $$\rho= \frac{n^{'}\sum M_c+\sum M_A}{V_c N_{AV}}$$ where $n^{'}$ is the number of formula units in unit ...
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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 ...
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Post-synthetic Anisotropic Wet-Chemical Etching of Colloidal Sodalite ZIF Crystals

It's well known that Metal-organic Frameworks can be made by attaching inorganic metal ions to organic linkers via strong chemical bonds, ZIF-67 is one of this big family which could be prepared by ...
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Fractal patterns on water

I stored water in a bucket (of aluminium probably), and some random fractal-like patterns are formed on the water: See here for some more pictures. Why this happened? I'm unable to reproduce it. ...
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What does stepped Ni(111) surface mean?

I think (111) surface refers to a flat surface of atoms that intersect with x,y,z axis at 1.
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Use of geometry index for the determination of coordination environment

Geometry index $\tau$ is supposed to resolve proper geometry for coordination numbers (C.N.) 4 and 5 based on its extreme values ($0$ or $1$). There is also a web app Geom which handles both cases for ...
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What causes the stairstep structure in bismuth crystals?

I've been interested in bismuth crystallization since I found out they existed, but have a question on their formation. According to Wikipedia, the stair-step structure of bismuth crystals is "the ...
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Number of atoms per unit cell

I don't understand the concept of unit cell and the number of atoms per unit cell in a cubic lattice also the calculations for the number of atoms. For example in the $\ce{fcc}$ lattice, number of ...
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What determines how much water of crystallisation a salt has?

Is there any reason behind the number of water of crystallisation? For example, $\ce{LiCl.2H2O}$ has two waters of crystallisation, and $\ce{MgCl2.8H2O}$ has 8 waters of crystallisation. Why does $\...
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How to get Jmol to automatically determine and display bond order?

Some molecule file formats do not detail bond order and when I open these formats in Jmol implied (by the valency, of course) double bonds are not shown as double bonds but rather as single bonds. Is ...
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Trioxane fuel tablet recrystalization

I had a bunch of old military trioxane fuel tablets. I decided to open all of the packets, maybe a dozen, and place the contents in an empty tin coffee can with a plastic lid. I put the can in a ...
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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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Why is the empirical formula of sodium chloride NaCl? [duplicate]

Since we know in sodium chloride crystal sodium ions are surrounded by $6$ chloride ions and each chloride ions are again bonded to $6$ sodium ions. What I want to know is that on what basis empirical ...
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Is this an aluminum screw dislocation?

Is this an aluminum screw dislocation? https://youtu.be/zbUPjHHml1E?t=55s I have heard of zinc pest which looks similar.
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Why is the buckminsterfullerene the purest form of carbon?

Other websites say that $\ce{C60}$ doesn't have surface bonds that are attracted by other atoms as in graphite and diamond. I understand that graphite may be attracted by other atoms because of its ...
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What is the volume occupied by the atoms and the edge length in these cubic lattices?

Consider a cubic unit cell of crystal that is composed of a single kind of atom. By placing atoms at every corner of the cube, a simple cubic lattice is formed. Assume that the atoms are perfect hard ...
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Schottky Defect in AB2 type crystals

Are there any examples of Schottky defect in ${\ce{AB_2}} $ type crystals. Does Schottky defect require that the cation and anion be of equal size? According to me it is not necessary that the two ...
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Limiting radius ratio

I recently came across this question while studying Solid State. The coordination no. of [Ni(CN)4]2- is 4 as Ni is bonded to 4 CNs and is planar in structure.Hence its Limiting Radius Ratio must be ...
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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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metallic bonding in transition metal sulfides

I searched on the internet but failed to find a clear solution for this question: Regarding transition metal sulfides like NiS or FeS, is there metallic bonding within their crystal structure? If ...
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Is the 'central Tin atom' in crystalline tin oxide really offset like this?

Is the position of the central Tin atom as shown in the first figure ($\ce{SnO2}$) drawn offset towards the oxygen to the right for a reason? The oxygen also seems to reciprocate and move towards the ...
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Why is the product of the reaction between iron and steam is iron (II, III) oxide and not iron (II) oxide or iron (III) oxide? [duplicate]

The reaction between Iron and steam in my textbook is given as this: $$\ce{3Fe + 4H_2O <=> Fe_3O4 + H_2} $$ My question is why these following reactions are not possible or do not happen. $$\...
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How many crystal forms of HCl have been identified - where to find the unit cells/lattice constants?

This blog about stomach acid shows this image of the "zig-zag" form of crystalline HCl (see also Wikipedia where it looks (to me) like five four HCl's per unit cell), but links to this cubic crystal ...
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Na(s) vs NaCl(s) Entropy

I would think the crystalline, ionic solid would have the lower entropy, however, the tablature indicates otherwise. Why does $\ce{NaCl(s)}$ have a greater entropy than $\ce{Na(s)}$?
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Why is ZnFe2O4 a normal spinel?

Considering that $\ce{Zn^2+}$ is $\mathrm{d}^{10}$, $\ce{Fe^3+}$ is $\mathrm{d^5}$, and $\ce{O^2-}$ is a weak field ligand, the CFSE values of both the normal and inverse spinel structures should be $...
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What is this blue crystal?

I was sorting out some old boxes in one of the rooms in my house, when I found a small container with about 10 grams of this blue crystalline powder. I assume that it contains some form of copper due ...
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crystallinity of seed crystals

Does the crystallinity of seed crystals affect the final crystal structure? and is it different depending on the crystallized material?
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Structure of lead(II,IV) oxide

I need help sorting out the molecular structure of tri-lead tetroxide, aka lead(II,IV) oxide $\ce{Pb3O4}$. This data sheet shows this image: The Wikipedia's lead (II,IV) oxide's link to a Jmol ...
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Can Isopropyl β-D-1-thiogalactopyranoside be degraded into either 1-deoxy-galactose or just galactose?

This may be a silly question, but is it feasible that Isopropyl β-D-1-thiogalactopyranoside (IPTG) when acted upon by a beta-galactosidase could produce 1-deoxy-galactose or just galactose? The ...
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How to compare the bond lengths of an peroxide complex before and after oxidation?

The complex $\ce{K6[(CN)5Co-O-O-Co(CN)5]}$ is oxidised by bromine into $\ce{K5[(CN)5Co-O-O-Co(CN)5]}$. In this we have to comment on the change on length of $\ce{O–O}$. But for that we have to ...
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How can I solve a non-cubic crystal structure?

Say I want to solve the crystal structure of barium sulfate, and I want to not only determine crystal type and the lattice parameter, but also the orientation of the oxygen atoms on the sulfate anion. ...
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Observing crystal of water

By just freezing water and using an optical microscope, can I observe water crystals? Or do I have to use a special light to see?
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Why are thermoluminescent materials mostly mostly based on calcium sulfate rather than on zinc sulfide or calcium fluoride?

I am doing a research in thermo-luminiscent topic and over a part of phosphor called calcium sulfate? The question my mentor asked to me is that why mostly people choose calcium sulfate to do research ...
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Relation between molecule symmetry and crystal symmetry

How much is crystal symmetry dependent on molecule symmetry? Can one make any kind of inferences on the symmetry of the molecule looking at the symmetry of its crystal or the other way around?
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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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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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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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Charge density is the amount of charge per unit volume but what is charge?

I was studying about x ray crystallography and my book says that charge density is measured in electrons per nano-meter cubed and this means that charge is the amount of electrons. But i am not sure ...
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How the crystal structure varying for the same compound?

i have synthesized the crystal Cyclohexylammonium acetate. Structure of this compound was already solved and it s under centro symmetric space group I2/a. But when i took single crystal analysis it ...
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What does β stand for in β-potassium zirconate?

What do the Greek letters (α, β, γ...) convey when they are prefixed to a crystalline substance? For example: β-potassium zirconate
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Is there a difference between Close Cubic Packing and Face Centered Packing?

I see some places use close cubic packing (ccp) and face centered packing (fcp) interchangeably. Are they the same thing? Does one provide more information than the other?
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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 ...