The first atomic bomb created ‘forbidden’ quasicrystal | Hacker News Reader

The first atomic bomb created ‘forbidden’ quasicrystal

discovermagazine.com

104 pointsdanboarder41 comments

Wow this seems to be a very exciting research field:

> Although more than 100 types of quasicrystals have been discovered since 1984, Steinhardt says that an infinite number of possibilities may exist — each with their own elastic, electronic, and photonic properties tied to the periodic ordering of their atoms.

> Steinhardt’s own research group has worked to create “photonic quasicrystals,” which act as semiconductors for light and form nearly perfect spherical symmetric band gaps. That feature is desirable in circuit designs and could be used in future computer and communication devices.

I would imagine that once you start blowing stuff up in zero G you'll get even more interesting results.

ie: https://en.wikipedia.org/wiki/Widmanst%C3%A4tten_pattern

A recent playfield for quasi-crystals have bee realized by making 30 degree twisted bilayer graphene. This playfield has been extended as well using stackings of any 2 different moire systems into one, with a 30 degree misalignmnent between the respective moire angles.

Are you sure? My understanding was that perturbations resulting from subatomic crevasses in multi-dimensional lattices would render the impedance greater than the Yui-Schwarz limit.

https://pubs.acs.org/doi/10.1021/acs.nanolett.0c00172

This was not the first work on this, but it's the first that shows with a quick Google search while in the subway.

Let me take some time to understand your comment.

In the meanwhile, the whole field of superlaticces got a great boost with the first realization of moire systems using hBN, graphene and the like in 2013(?) by P. Kim and others. Before that, indeed, patterning superlattices from the bottom-up had been a laborious and mostly failing endeavor. If that's what you are referring too...

I have a feeling they were taking the piss

This made me visualize the periodic table of elements as a 3d stack of cubes, with a cross section of properties conferred by making various crystals out of the pure elements.

I just happened to come across this fascinating video[0] yesterday that explained the same thing. And he mentioned the crystal as well.

[0] The Infinite Pattern That Never Repeats: https://youtu.be/48sCx-wBs34

Great video thanks for sharing. My brain still hurting, it tried to explode at 14.38 :-)

https://youtu.be/48sCx-wBs34?t=878

Also quite interesting these are found in a few meteorites. I wonder if somebody is confidentially keeping some quasicrystal with very special properties somewhere.

"Third-ever natural quasicrystal found in Siberian meteorite"

https://www.newscientist.com/article/2115570-third-ever-natu...

It seems many here did not like the fact I did not know and find completely obvious, the fact that a Fibonacci sequence is a fundamental example of a 1D quasiperiodic structure exhibiting aperiodic long range order :-))

> quasicrystal materialized in temperatures above 2700 degrees Fahrenheit and pressures of 5000 to 8000 pascals. To you and me, it would feel similar to [...] someone carrying thousands of elephants [...] stands on your back.

Hmm, from my mechanical engineering times, 8 kP does not sound like a big deal at all.

Say it's 5 tons per elephant, which would be about 50kN. A human foot is about 25 cm long, and I guess two of them might be about as wide, so 0.0625 m^2. Pressure is force over area, so 800 kN/m^2, or 800 kP. That's per elephant.

I'm going to assume the article is missing a "mega" somewhere in there.

Given that atmospheric pressure is around 100,000 pascals, yeah they're probably missing some SI prefix.

Edit: The original article talks about pressures of 5 to 8 GPa. [1]

[1]: https://paulsteinhardt.org/wp-content/uploads/2021/05/BindiE...

Reading those Fahrenheits and pascals in one sentence really hurts.

For anyone not in USA (or the tiny handful of other countries still using it), Fahrenheit hurts to read full stop.

I don't think Celsius can be considered less arbitrary, and the anthropocentricity of Fahrenheit has its advantages. I would honestly be happy to give up Celsius if in exchange the US et.al. moved over to metric distances.

That then would be the foot in the door for eventual full metric conversion!

I agree Celcius is also entirely arbitrary, any scale would be really, but when 95% of the world's population uses Celcius (and the metric system has similar worldwide usage) perhaps it's time for them to go with the consensus.

boiling water is 100•F. freezing water is 0.

what’s not to like about this human-perspective?

Why yes. Running a fever is dangerous because that's exactly the point where the blood starts to boil. Let it simmer too long and smoke comes out of your ears.

centigrade surely?

Not if you're a human describing their environment: zero is F.cold and 100 is about as hot as you can stand.

That's not much of an advantage if you haven't grown up with it. It's also very arbitrary in that it doesn't account for preference or acclimatisation.

EDIT: or humidity, which is also going to be a major factor in how much you can stand.

37°C is fine in my opinion, just drink enough water and don't stand in the sun.

The official Fahrenheit scale is something that only USA can love.

Hmm, 100 for human body temperature is good, but 0 for the lowest temperature achievable in a lab 300 years ago is not so good.

The Aspden scale has its zero at water-freezing and 100 at this-will-kill-you-if-you-can't-sweat. 50A is "nice". It's really intuitive and perfect for weather reports. For science, use Kelvin of course.

>but 0 for the lowest temperature achievable in a lab 300 years ago is not so good.

It's approx the temp that sea water freezes at. That's not useless.

212-32= 180 degrees between fresh water freezing and boiling.

The metric system has its merits, but US units aren't as arbitrary or pointless as people think. It may not be made for decimalization, but it does feature units that are easily divisible by even numbers and 1/8ths.

It's a balance between useful approx characteristic points and convenient divisors.

And based on how many people struggle with knowing where to put the decimal (or use the correct prefix) in metric, I'd argue decimalization isn't the great "simplification" it's made out to be.

And the fact that people think the decimalization of time would be crazy is proof that it's more about familiarization than simplicity.

Yeah, I can't stand freezing nor boiling either! Let's go ahead and embrace a better unit of measurement now!

What if some humans have different temperature preferences? Do they get a different temperature scale to suit them?

Temperature doesn't really exist. It is a concept for describing the kinetic energy of molecules. So we could go with some combination of meters/seconds/mass/atomic mass. We could call it the ped-kelvin, the temperature scale only used by the most pedantic of scientists.

This sounds like you're trying to reinvent the Boltzmann constant without quite knowing what it is.

(and without quite knowing what temperature is, but that's besides the point)

As I said, a scale for the most pedantic of scientists. I and everyone else who took physics in highschool is well aware of Boltzmann's work.

Surely m*s as the average speed of molecules you are measuring would be the sanest.

Temperature is a measurement of kinetic energy, speed x mass. Two substances with the same temperature can have different m/s atomic speeds. Moving at the same speed, Uranium atoms will be 'hotter' than hydrogen atoms because the uranium atom is heavier.

(This distinction is important in rocketry. At a given exhaust temperature, the lighter substance will be moving faster, resulting in greater efficiencies.)

Oh right. I completely forgot about the mass of the individual atoms.

So basically:

(Sum of the speed * mass of (from atom[1] to atom[total number])) divided by the total number of atoms?

As a complete tangent, I recently heard a podcast [1] with Frank Wilczek, inventor of so called time-crystals, where he discussed materials where waves can propagate according to a rich enough set of rules to essentially "simulate" another world with its own set of physics. Fascinating.

[1]: https://youtu.be/0zAlEjFU7xo?t=3000

What would be most interesting about these quasicrystal characteristics are: 1. tensile strength 2. cleaving strength 3. torsional strength

We have got starships to make that need to handle these upcoming warp engines.

Just looking ahead here.

I am not a physicists.

I wonder if those properties would not be uniform across the quasicrystal because of it’s non-repeating pattern.

The article concludes by suggesting that people will create more quasicrystals in labs, with various desired properties. That seems reasonable. What I didn’t understand is this line:

> And the more mathematically perfect they are, the less electrically conductive.

Anyone understand what “mathematically perfect” means here, or why that implies reduced conductivity?

I would have imagined it is used in the same way it is used for crystals. Mono-crystals are considered mathematically perfect, while poly-crystals (with their grain-boundaries separating different cyrstal orientations) are less perfect. So, for quasi-crystal, the patterning which follows a set of mathematical rules (although lacking translational invariance), can be interrupted, thus being "mathematically less perfect".

Now as to why that implied reduced conductivity... thinking in terms of Bloch waves, they require periodicity. In absence of Bloch waves that describe the electron density probability, the electrons are considered to be localized (e.g. as in the Landau level description of electrons implying localization of electrons in a perfect crystal). So for perfect quasi-crystals, this periodicity is fully absent, thus they are localized too. The latter hand-wavy argument is just speculation of mine...

I'm not sure if my guess is right but my understanding is that "mathematically perfect" is related to how close to actual crystals they are. For example the Penrose tiling in the picture is made of tiles of 2 different types, so it's more "perfect" than another pattern that would use 3 different types of tiles, etc.

> To you and me, it would feel similar to lying inside a volcano while someone carrying thousands of elephants (presumably stacked vertically) stands on your back.

Finally, a journalist using units of measurement I can relate to.

Oh, so now they’re ‘forbidden’? A few months ago they were only ‘impossible’.[1] I saved the article (which also was here on HN) at the time because it contains the conceit “science does what puny humans say is impossible,” but the people who say things are impossible are scientists themselves. Are we supposed to be impressed by that? Plagiarists, AKA journalists, get paid to copy other people’s work. Come to think of it, that’s what Stack Exchange is for, too…

[1]https://www.nature.com/articles/d41586-021-01332-0

Much like the Colonel's 11 Secret Herbs and Spices, they are both Forbidden to know, and Impossible to understand.

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