X-ray crystallography

It comes up on an XRF scanner as limestone material-wise or SEM, but it's not.

You look at the XRD and the SEM results of this stuff, and it's foreign.

It's very, very strange.

And so finally, of course, we're looking at the artifact aspect of this and how people say, oh, you can't take artifacts out of countries, right? Well, the policy of Mexico has been for years, right? Oh, these are just tourist attractions, tourist things.

Okay, so in our lab, uh, phase transitions come about usually because we mix the precursors that are different, um, crystals basically, but then we r- raise the temperature or do something else to encourage them to react, and then atoms start reacting, and they form into this new crystal.

Um, and the, this shows up in the XRD pattern because usually if the geometry of the atoms change drastically, the XRD pattern changes a lot.

But what really happens in, like, a typical practical materials discovery campaign is when you first try something, it doesn't work, and the outcome isn't just, like, a clear yes or no, but it's usually, like, a very mixed phase.

Uh, it will usually have some of the precursors.

So the simulations can always say, "Oh, this phase doesn't look like what we predicted, but this is a slightly variat- variation of it.

Let me now do force field calculation to see if it's still stable." Or like the AI can say, "Based on the previous experiment and this one, this is probably not the phase we wanna make, so let's change the conditions."

Yeah, for, for listeners, XRD is X-ray diffraction, which you already described.

Yeah.

And at some point you put it in a characterization instrument.

For inorganic crystals, the method we use the most is an XRD, X-ray diffraction.

It's the same X-rays you get at the dentist.

It just happens that X-ray wavelength is of a comparable length scale as the distance between atoms.

And then if it succeeded, maybe you want to see if it's a superconductor.

So then you put it in another instrument that can measure the diamagnetic response, which tells you if it's a superconductor at a given temperature.

Yeah, I think the XRD is a really interesting example, too, because the materials don't come out labeled.

Yes.