
At high pressures, potassium adopts a mix of crystalline and liquid structure - evo_9
https://www.nationalgeographic.com/science/2019/04/new-phase-matter-confirmed-solid-and-liquid-same-time-potassium-physics/
======
apo
It's great that the popular press still runs science articles.

What's not so great:

1\. There is no link to the original paper.

2\. The description of the phenomenon has been so contorted that it's
impossible to understand exactly what was found or its significance.

The article notes:

> “Somehow, these potassium atoms decide to divide up into two loosely linked
> sub-lattices,” Hermann says. But as scientists turned up the heat, x-ray
> images showed the four chains disappearing, and researchers argued about
> what exactly was happening.

Fine, there's debate about how to explain the experiment.

> The computer models confirmed that between about 20,000 and 40,000 times
> atmospheric pressure and 400 to 800 Kelvin (260 to 980 degrees Fahrenheit),
> the potassium entered what’s called a chain-melted state, in which the
> chains dissolved into liquid while the remaining potassium crystals stayed
> solid.

That's just one explanation consistent with the data. Clearly, there are
others.

The article gives the false impression that some smoking gun has been found.
Far from it.

------
snazz
How can a computer model prove the existence of something physical? Wouldn’t
it have to occur in real life before they can make this claim?

~~~
gus_massa
I can't read the research article now, but from the press article, it looks
like they are explaining a known experimental result that was unexplained (or
confusing) until now.

IIUC in a previous real life experiment other group put a tiny amount of
Potassium under very high pressure, and they uses x-ray diffraction to "see"
the structure of the sample. At low temperature they saw regular arrangement
of atoms that has slots (like a "sponge", but a regular sponge). In these
slots there were more atoms in some fixed positions.

When they increase the temperature, the "sponge" part didn't change, but the
atoms in the slots began to move like in a liquid. In the x-ray you get sharp
point for the atoms that are essentially still and in a regular arrangement
(the points are not the atoms), but the atoms that can move or are in
irregular positions don't produce sharp point.

So IIUC in a previous real life experiment other group saw a change. My guess
is that the atoms that can move don't drip. They keep trapped inside the
"sponge" part (like a small amount of water in a towel). The dripping part is
probably a bad metaphor.

\---

In spite we know all the quantum mechanic rules to simulate this, the problem
is that the runtime grows exponentially with the number of atoms. So an exact
simulation is only possible with only a few small atoms (5-10 Carbons, perhaps
10-20 Hydrogens (but not 10 Carbons and 20 Hydrogens). Potassium has a lot of
electrons, so it is more difficult.) (And the simulation is not as exact as a
Mathematician would like to call it exact.)

There are some tricks to avoid the exponential time. Like assuming that the
atoms/electrons only interact with nearby atoms/electrons. It's quite true,
but not 100% true. You can also use some model of how the electrons in one
atom interact with the electrons in the other atom. But electrons like to
wander, specially inside a conductor, so you must consider the electrons that
live between the atoms. It's a lot of fun, there are plenty of model to
approximate how the electrons behave in some situation, but each model is good
for one situation and bad for other situations.

If you want to go down the rabbit hole
[https://en.wikipedia.org/wiki/Density_functional_theory](https://en.wikipedia.org/wiki/Density_functional_theory)
, but it is not the only method to try to solve the problem. There are a few
rabbit holes, because the exact problem has exponential complexity.

In this work, they use a neural network to approximate the behavior of the
electrons in each atom (and between atoms). I guess that they are assuming
that they interact almost locally, and hopefully they can get the result in
linear time instead of exponential. I'm not sure if this can be classified as
DFT or other technique, or they are digging a brand new rabbit hole.

It's difficult to judge the work by reading only a press article, but the
abstract of the research paper says:

> _Calculations necessitated the development of an interatomic forcefield
> using machine learning, which we show fully reproduces potassium’s phase
> diagram, including the chain-melted state and 14 known phase transitions._

It looks very promising, specially because in each phase the conditions are
different and that makes the use of a single model very difficult.

~~~
DannyBee
I wrote a computer program which proves this article is wrong.

It avoids exponential runtime by assuming that because newspapers mostly make
a mishmash of science articles, that you only need to look at some of the
words before deciding whether they made a mishmash of this article. It's not
100% true, but it's quite true.

...

~~~
gus_massa
Great. When you get it published in a peer review journal, please post it here
so we can discuss it.

------
peter_d_sherman
Favorited.

If you were interested in one day creating Star Trek's Replicator, this might
be a good place to start. That is, here might be a good place to study the
junction between solid and liquid phases of matter (your future Replicator
would probably create liquids out of thin air before you figured out how to
create solids, and this might be the phenomena you wanted to study to then
figure out how to create those solids...)

Also, the list of exotic states of matter in the article is worth reading and
re-reading...

~~~
ArnoVW
If you're an amateur of exotic states, try
[https://en.wikipedia.org/wiki/Time_crystal](https://en.wikipedia.org/wiki/Time_crystal)

~~~
selimthegrim
It’s not an equilibrium state so is different from the others.

------
KeatonDunsford
I recently enjoyed reading Dr. Gerald Pollack's "The Fourth Phase of Water:
Beyond Solid, Liquid, and Vapor". I wonder...

[https://www.amazon.com/dp/0962689548/ref=cm_sw_r_cp_awdb_t1_...](https://www.amazon.com/dp/0962689548/ref=cm_sw_r_cp_awdb_t1_HtYLCbAP0ZJDD)

------
DiseasedBadger
Reminds me of the sodium amalgam Nile Red was experimenting with on his last
video (other than the April Fools one).

It seemed to be a sponge of liquid mercury dissolving liquid ammonium.

------
Sniffnoy
Why on earth should we trust (for such things) a model that includes an opaque
neural network?

------
itissid
Shouldn't plasma be also listed as a state of matter in the opening sentence?

~~~
Semaphor
They list 6 other states of matter at the end, including plasma.

------
Causality1
Clickbait title. The discovery is that at high pressures, potassium adopts a
complex crystalline structure, of which different parts have different melting
temperatures.

~~~
dang
Ok, we'll use that. If anyone can suggest a better title (i.e. more accurate
and neutral, preferably using representative language from the article itself)
we can change it again.

~~~
gus_massa
The melting part is important. It's not just a complex crystal structure. If's
a crystal structure with slots that are filled with the same material. The
interesting part is that the filling and the main crystal structure have a
different fusion temperature.

" _At high pressures, potassium adopts a mix of crystalline and liquid
structure_ "???

~~~
dang
Done. Thanks!

------
metaphyze
Sounds like someone has discovered cats.

~~~
dang
Please don't do this here.

------
Myrth
"bizzare" state lol

some day mainstream scientism will realize that it is impossible to
extrapolate global reality from local perceptions...

~~~
SketchySeaBeast
Isn't that what science is based upon though? We can only make assumptions
based upon observed results. You can extrapolate and then test based upon
those extrapolations, and we can acknowledge that there are gaps, but I don't
think someone saying "wow, that didn't meet my expectations at all" in any way
discredits science.

------
crimsonalucard
While the material discussed in the article and new, the phase of matter is
not new. The term is called non-newtonian fluid. Believe it or not you can
make material with these properties in your own home.

An inexpensive, non-toxic example of a non-Newtonian fluid is a suspension of
starch (e.g. cornstarch) in water, sometimes called "oobleck", "ooze", or
"magic mud" (1 part of water to 1.5–2 parts of corn starch). The name
"oobleck" is derived from the Dr. Seuss book Bartholomew and the Oobleck.

Because of its properties, oobleck is often used in demonstrations that
exhibit its unusual behavior. A person may walk on a large tub of oobleck
without sinking due to its shear thickening properties, as long as the
individual moves quickly enough to provide enough force with each step to
cause the thickening. Also, if oobleck is placed on a large subwoofer driven
at a sufficiently high volume, it will thicken and form standing waves in
response to low frequency sound waves from the speaker. If a person were to
punch or hit oobleck, it would thicken and act like a solid. After the blow,
the oobleck will go back to its thin liquid like state.

~~~
derekp7
I wonder if something like that would work in a ballistics armor application?

~~~
ghaff
Not ballistic armor but D3O is one material used for impact protection that is
flexible but becomes rigid when there's an impact. (I have a ski hat with ribs
of this material.)

