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35 votes
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Contribution of Tetrahedral and Octahedral voids in HCP

I cannot find anywhere.. Couldn't find? You can figure it out on your own, with me, right now. Disclaimer: By "hexagonal unit cell" I assume you mean hexagonal prism, which comprises of 3 primitive ...
William R. Ebenezer's user avatar
29 votes

How can brass still be made even though the crystal structures of zinc and copper are not the same?

The $\ce{Cu-Zn}$ phase diagram is, to put it mildly, complicated. (source) See that wide area denoted $\alpha\rm (Cu)$? Now, when we add a little amount of one metal into the crystal lattice of ...
Ivan Neretin's user avatar
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21 votes
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What makes Gorilla Glass more durable with each generation?

Are there other ways of "chemical strengthening" besides cationic exchange that can be utilized to strengthen the glass, keeping it flexible and less fragile at the same time? In a word: No. To ...
A.K.'s user avatar
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17 votes

How to calculate the height of an hcp lattice?

To calculate the height of a unit cell, consider a tetrahedral void in an hexagonal closed packing arrangement. It can be imagined as a 3 solid spheres touching each other and at the center-point, you ...
Berry Holmes's user avatar
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17 votes
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Will a solid object lose or gain atoms on standing over time (without being acted upon by external influences)?

Short answer: Yes they do. Firstly, you need to arrive at a proper definition for an "object". Why you ask? Because it would otherwise present philosophical problems which become apparent when we ...
paracetamol's user avatar
  • 18.7k
16 votes

How are the number of tetrahedral voids twice the number of octahedral voids in a CCP structure?

To be precise, if in a close packed structure (ccp or fcc) there are $n$ atoms or ions then the number of octahedral voids and tetrahedral voids will be $n$ and $2n$ respectively. For example, there ...
Mitchell's user avatar
  • 1,108
16 votes
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For a given packing (hcp, fcc, bcc), which ions occupy the corners and which occupy the faces or centers?

The actual answer is that it doesn't matter. For many of the 1:1 solid-state structures, either the cations or the anions may be considered to be at the vertices (i.e. corners) of the unit cell. By ...
orthocresol's user avatar
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14 votes

How can brass still be made even though the crystal structures of zinc and copper are not the same?

While molten, copper and zinc (and tin) are miscible. As the alloy cools and crystalizes, the metals do indeed separate, forming grain boundaries. These inclusions "pin" slippage between ...
DrMoishe Pippik's user avatar
13 votes

What does β stand for in β-potassium zirconate?

They signify one polymorph (the beta polymorph) of barium zirconate. Allotropy is the property of some chemical elements or compounds to exist in two or more different forms in the same physical state ...
Nilay Ghosh's user avatar
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12 votes

What is "chemical pressure"?

External and internal pressure To study the effect of pressure on properties of a solid, is equivalently to learn how changes in volume transform physical parameters. For external pressure at ...
Linear Christmas's user avatar
11 votes

Calculate the third and fourth nearest neighbours in bcc

You can think of the body centered cubic lattice as two simple cubic lattice, one with points at coordinates $(ma,na,pa)$ where $m,n,p$ are integers, the other with points at $((m+(1/2))a,(n+(1/2))a,(...
Oscar Lanzi's user avatar
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10 votes

Why are p-type solar cells more prone to degradation in space than the n-type ones?

The space radiation environment is a quite complex subject. Generally speaking one needs to be careful about just where in space you are concerned about - near earth orbit (within the Van Allen Belts),...
Jon Custer's user avatar
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10 votes
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Calculate the third and fourth nearest neighbours in bcc

With $\sqrt3\over2$ being that close to $1$, BCC packing is better not looked at in terms of coordination spheres. But if you insist... Say you are sitting in the center of a cell. Then: Your first ...
Ivan Neretin's user avatar
  • 31.2k
10 votes

How do I know crystal structures from formula?

I'll just point out the direction in which you could look for an answer. In general case, it should be almost impossible to determine the crystal structure by looking at the chemical composition of a ...
voffch's user avatar
  • 783
9 votes

Distance between successive tetrahedral voids in FCC

As shown in figure, if we divide a FCC unit cell into 8 small cubes, then each small cube has 1 Tetrahedral void at its own body centre. Thus, there are total 8 Tetrahedral voids in one unit cell. It ...
Jay Chudasama's user avatar
9 votes

What does β stand for in β-potassium zirconate?

Some inorganic crystals show the property of structural polymorphism where two or more crystal polymorphs exist. These polymorphs may differ either by position of metal ion or ligand (or other ion ...
ankit7540's user avatar
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9 votes
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What is the reason for isotropy in amorphous solids?

Assume that the spheres in the drawing are atoms. In the second picture atoms are not orderly arranged. No matter where you go in crystal of a amorphous solid, the disarrangement will be same. Since ...
Divyansh Jain's user avatar
9 votes
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Why we don't talk about unit cells in hcp/fcc structures?

We do not remain silent about the unit cells in this context. The hexagonal close packed structure is called so because it has hexagonal unit cell, and the other one is called fcc precisely because ...
Ivan Neretin's user avatar
  • 31.2k
9 votes

Calculating the strength of an ionic bond that contains poly-atomic ions

With enough effort, Born–Haber cycle can be extended to polyatomic ionic solids, however it's practically never done in practice due to the lack of experimental data or because it's impossible to ...
andselisk's user avatar
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9 votes
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Software for generating a lattice from a unit cell for molecular crystals?

In addition to the presentations about CCDC Mercury and Vesta by @andselisk here and later mine about Avogadro could be extended. As described earlier, Avogadro's capability to read .cif files about ...
Buttonwood's user avatar
  • 30.1k
9 votes
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Structure of crystalline boron trioxide

This statement is relevant for the initially [incorrectly] determined structure of $\ce{B2O3}$ by Berger [1, 2] who used powder x-ray diffraction data. You can still access the structure and visualize ...
andselisk's user avatar
  • 38.1k
9 votes
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Why does Xenon Hexafluoride exist as [XeF5+][F-] and not [XeF5+][XeF2-] in the solid state

First and most obviously, if something in solid state forms ions by shuffling atoms around, the end result must yield the same ratio of atoms. Take for example $\ce{PF5}$: this exists as $\ce{[PF4+][...
Jan's user avatar
  • 68.2k
9 votes

Why are there exactly 5 types of two-dimensional lattices, and what distinguishes them?

First, about the black lines. I think they are helpful for the hexagonal and the rhombic lattice. For the hexagonal system, it shows you the hexagons. One hexagon contains exactly the same space as ...
Karsten's user avatar
  • 40.7k
8 votes
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What are some materials that expand a lot proportionally to heat?

You are looking for thermal expansion and its coefficient. Of course such tables, and diagrams exist (source) as it is of relevance in daily live. Thermometers based on liquid mercury, or alcohol, ...
Buttonwood's user avatar
  • 30.1k
8 votes

Why doesn't tantalum and tungsten form amalgam?

Imagine a lump of a metallic element in close contact with an equal amount of liquid mercury. Amalgamation might proceed to some degree if the metallic element has an even higher surface tension than ...
James Gaidis's user avatar
8 votes

Why is sea salt coarse?

The method of production of sea salt usually involves bulk evaporation of seawater. This allows the salt to crystallise and due to it's bigger size it is sold without much processing. On the other ...
Desai's user avatar
  • 471
8 votes

Why is diamond not the most dense substance?

There is no general relation between hardness and density. One thing is the packing and bonding character ( what matters mostly for hardness), other is the idealized atomic ball radius and the atomic ...
Poutnik's user avatar
  • 42.3k
8 votes
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"Fireblob" in KO₂ and PCl₅ reaction

Here's my best guess at the play-by-play. $\ce{PCl5}$ is a solid with a relatively low melting point (160 °C) and high volatility (sublimes at 167 °C). When the solid $\ce{KO2}$ gets dropped on the $\...
Nicolau Saker Neto's user avatar
7 votes

What makes Gorilla Glass more durable with each generation?

To really answer this, you need to characterize the glass in terms of its properties, and not something like its ability to resist being scratched. Scratch resistance is a behaviour, and not a ...
AlanJ's user avatar
  • 254
7 votes
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Number of atoms per unit cell

The denominator signifies the number of cubes that are needed to completely encompass the whole point. For example, a corner point can be thought of as a center of 8 whole cubes, while a face centre ...
Ayushmaan's user avatar
  • 1,132

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