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 ...
- 30k
28
votes
Accepted
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 ...
- 2,655
26
votes
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Why are there no cheap diamond equivalents?
There are four properties that make a diamond look like a diamond. I will compare them with the two best diamond simulants at the moment:
cubic zirconia $\ce{ZrO2}$ - a special ("cubic") form of ...
- 5,004
20
votes
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Why are there only 7 types of unit cells and 14 types of Bravais lattices?
All quotes will be from Solid State Physics by Ashcroft and Mermin.
Bravais Lattice:
A fundamental concept in the description of any crystalline solid is that of the Bravais lattice, which ...
- 7,650
20
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 ...
- 11.9k
17
votes
How to solidify sand
Based on your comments, it sounds like you have some sort of colored sand and you want to immobilize it. My suggestion would be some sort of polymer matrix.
There are multiple possibilities, but one ...
- 26.9k
17
votes
Why are there no cheap diamond equivalents?
There are plenty of synthetic materials that would fall into the "cheap diamond equivalent" category. If we're only talking about the optical properties, cubic zirconia ($\ce{ZrO2}$) is probably the ...
- 12.6k
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 ...
- 3,996
16
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 ...
- 18k
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 ...
- 65.8k
15
votes
Why is solid phase peptide synthesis limited to 70 amino acids?
The issue is one of yield. Each step has a certain yield percentage of yield, that the synthesizers will maximize as much as possible. However, given that it is fairly impossible to generate 100% ...
- 2,035
15
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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 ...
- 1,078
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 ...
- 24k
13
votes
Why is solid phase peptide synthesis limited to 70 amino acids?
You need to perform one reaction per amino acid to couple it to the previous one, and that reaction isn't 100% efficient. You always get a small amount of unreacted peptide, or some other side product....
- 5,908
12
votes
How to solidify sand
Geologists prepare soil profiles for a living. The task is easy in principle - dig a pit, apply glue to the wall, then transfer the glued layer to a sheet of cloth. The practice is really difficult, ...
- 2,368
12
votes
What does β stand for in β-potassium zirconate?
They signifies 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 ...
- 22.3k
11
votes
How does chromium help stainless steel prevent rusting?
TL;DR
Note that the passive layer forms on the surface, there needn't be any change to lattice constant. Chromium needn't migrate , the Cr present on the surface will form the layer to protect it....
- 1,241
11
votes
Accepted
Why are X-rays used in crystallography?
There are a few reasons, but the most direct answer is that the wavelength of X-ray photons is on the order of the distance between atomic nuclei in solids, e.g. ~ 4 ångströms (bonds are roughly 1.5-2....
- 3,514
11
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 ...
- 6,851
10
votes
How to solidify sand
I upvoted the water idea, after all it is possible to build sandcastles over 0.2 m high with just water as a binder. I also think coring as mentioned in that answer is a good idea. I also upvoted the ...
- 1,639
10
votes
Accepted
Are all lattices Bravais lattices?
From Ashcroft and Mermin's Solid State Physics:
A fundamental concept in the description of any crystalline solid is that of the Bravais lattice, which specifies the periodic array in which the ...
- 7,650
10
votes
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Yellow color of NaCl
An F-center (or any color center) is a point defect in the material that generates localized electronic states. When these states are in the band gap, they will result in strong peaks in optical ...
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10
votes
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Materials with solid volume greater than liquid volume
There is a bunch of such materials; among the elemental compounds, they include silicon, gallium, germanium, and bismuth. As for the properties... well, it just so happens that their crystal structure ...
- 30k
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),...
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9
votes
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What causes photovoltaic (solar) cells to degrade?
Why do they degrade? What exactly is reducing their efficiency?
This link outlines several modes of solar panel degradation, and this report by the National Renewable Energy lab is a very detailed ...
- 10.1k
9
votes
Why do different impurities create different colors in diamonds?
If you had googled a little bit you would have found this wonderful resource.
In a yellow diamond, a few carbon atoms per million have been replaced
by nitrogen atoms, each containing five ...
- 17.3k
9
votes
Accepted
What is the actual reason behind PCl₅ existing as an ionic solid?
In the gas phase ions cannot be stabilized through solvation or lattice forces so ions are destabilized relative to non-ionic entities in the gas phase. $\ce{NaCl}$ is a case in point, in the gas ...
- 82k
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 ...
9
votes
Are molecular optimizations in quantum chemistry really in vacuum?
You raise an excellent question and the short answer is "yes, quantum chemistry calculations are intrinsically in vacuum".
Approximate methods like semiempirical (AM1, PM6, PM7) and hybrid DFT ...
- 26.9k
9
votes
Accepted
How can diamond have a fixed refractive index?
Your textbook is wrong. Some crystalline solids are optically anisotropic. Many crystalline solids are indeed optically isotropic in nature. In solids like this the light beam experiences the same ...
- 5,004
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