Atomic resolution video of salt crystals forming in real time | Hacker News Reader

Atomic resolution video of salt crystals forming in real time

phys.org

113 pointsneltnerb34 comments

This reminds me of my first time using a microscope. I was on a course on mushroom identification and we were looking at spores and other microscopic features.

I was so surprised when I saw shapes in the viewfinder that didn't look organic. There were squares and pyramids, it looked like Aztec ruins. And they were growing before my eyes! I then realised it was the reagents crystallising in the heat of the lamp.

The world of microscopes is like magic, it's a shame that more people aren't exposed to it.

Even just a quality 10x hand lens opens up a whole world of detail that we don't usually see.

Good used microscopes are so cheap now. If I had a child, it would be on their desk early, like kindergarden.

Any suggestions for models to be on the look out for? I bought some generic plastic $45 CAD kit that’s good enough, but would love to have an idea of what to focus on next.

If you want something a bit DIY but very capable, check out the openFlexure scope. It's a 3d printed body to which you can add an objective and it has a 3d printable micropositioning stage and Pi camera mount.

Check out the foldscope

Atomic resolution real-time video at 25 frames per second!!! Holy cow! I mean, the nanohorns and salt crystal study is cool and all, but the real time video!? That's mind blowing, the kind of stuff we saw on Star Trek: The Next Generation.

"growing"

Expected video to show process of atoms slowly forming together or something to shape my mental model.

What I got was a full-formed grid of little atom things that just seemed to spring into existence between two frames.

It's still cool. But I am not less confused.

My guess is that individual atoms entering and leaving the formation happens on a much faster timescale than the formation switching between quasi-stable states.

It's almost as-if there are mini phase-transitions between formation sizes, it's fascinating.

Both modes are possible, if I read it correctly (see the bottom half of the first figure). Pieces of the lattice can "spring" into existence very quickly-- that's a phase transition. But, once formed, it can also "grow" atom by atom.

The individual atoms are much more mobile than the crystalline structure here. They are probably moving way too fast to be captured on a time scale that the crystal grows.

Think in terms of trying to make video of a tree growing and expecting to see individual water droplets falling from the sky.

You can infer the droplets must be there (as the ground would otherwise dry out and the tree die) but it is not possible to have a video of tree growing sped up so that a human can see it growing but also show water droplets falling from the sky.

The video is at atomic resolution. The dots in the crystalline structure are individual atoms.

To do this in realtime video is bonkers.

It is bonkers. But the only way we can even have that video is because the molecules are being frozen in the crystalline lattice.

As far as I know there exists no recording of actual molecules in a liquid (except maybe for something extremely viscous).

The video reminds me this photo: https://petapixel.com/2010/10/27/first-ever-photograph-of-a-...

It shows first ever photo of a human being on a busy street.

But you would not be able to say so, because the street looks completely empty.

The only way we can even see the person is because they stood still for long enough to leave imprint. Other than this one person, everybody else on this busy street moved so fast there is no recognizable imprint of them left. Hence the street looks empty.

Gotcha, I misunderstood - thought you were referring to the scale of the raindrops relative to the tree, not the speed. The photo's a better analogy (and cool).

This much is clear. The post above answers the question of why we can't see atoms that are not part of the lattice.

From the article it seems like the 'springing into existence' is a process called nucleation: https://en.wikipedia.org/wiki/Nucleation.

The grid appears suddenly, but strips of atoms keep piling on like those magnet ball toys, and it looks like it grows too big for its containment.

Maybe it grows slower as it gains more surface?

I think the trouble is that the time scale you've assumed for molecular reactions is off; atoms move and react much faster than you may expect. (In air at room temperature, an individual molecule will undergo billions(?) of collisions per second.) The atoms and molecules in this video are moving on the order of 200 m/s, and the image is only about 5 nm wide. To see atoms slowly forming together, you need to watch on the scale of picoseconds at a time, not the 20 ms - 40 ms per frame in this video.

A molecular dynamics simulation might give a better impression of the time scale: https://www.youtube.com/watch?v=FK29kxMSqH8&t=2m45s. (I'm not sure what volume is being simulated there. It's much larger than what's seen in the submission, which is about 18 water molecules wide if we assume water molecule size of 0.27 nm.) Note the time scale on the left. The whole simulation is 250 ps, so you have to watch it about 100 million times to match a single frame in the submission's video.

I believe this is from last year, I remember those little squares from a past life.

EDIT: January 12, 2021 - looks like my brain isn't fully swiss cheesed yet after all

Questions for any chemistry geeks present.

Seeing this, my immediate thoughs are:

- Any "salt water" solution we experience is likely not actually salt crystals in water, but ionic Na+ and Cl-. And when we produce salt through evaporation, that's actually the process shown in this video occurring, with fresh crystals of salt forming from the brine.

- What we taste as "salt" isn't actually the taste of salt, but of an Na+ + Cl- ionic solution, dissolved in our saliva. I'm not even sure we could physiologically taste salt itself, but it would likely not be the same.

Any validity to either of these thoughts?

I know it's just from this year, but January feels like a long time ago.

How could they tell from the video which atoms were Na and which were Cl?

I think it’s a combination of atomic radius and Z contrast (heavier atoms show differently from lighter ones in the TEM). It also helps that the crystal structure is known

They also describe some comparison to forward modeling in the methods section, which is cool

https://pubs.acs.org/doi/suppl/10.1021/jacs.0c12100/suppl_fi...

Is there a link to just the video anywhere?

https://scx2.b-cdn.net/gfx/video/2021/crystalclose.mp4

Previous discussion:

> Atomic resolution video of salt crystals forming in real time (u-tokyo.ac.jp)

> 664 points by rbanffy 8 months ago | 125 comments

https://news.ycombinator.com/item?id=25874497

I wonder if there is a (filter/algorithm/idk) that can recognize the noise in the video and remove it, leaving only the outline of the nanohorn and the crystals.

20 seconds? I thought molecules speed through a thousand cells in a fraction of a second!? How come the formation of salt in this setting is so (relatively) exorbitantly slow?

While we don’t have flying cars, watching single sodium and chloride ions forming crystals in 25 FPS surely makes me feel like living in the future, finally.

Looks so neat. I hope people from SaltStack will see this

at what point does the observing affect the observation?

I think in this case the surface interaction effects with the nanotube are likely to be much bigger

When she shuts the blinds and calls the cops.

This is lewd but funny, I needed that laugh.

Reply on news.ycombinator.com