The quantum mechanics of bling


Some say diamonds are a girl's best friend. I'd say they're a physicist's best model material.

Diamonds are crystals, unlike Swarovski "crystals" which are not crystalline at all. They're just fancy cut lead glass. How do you spot the difference? By shooting x-rays on them, of course.

See, being a crystal means there's a motif of atoms repeating regularly in space. Diffracting x-rays on this pattern will give a spectrum with sharp peaks. Being a glass means atoms are not ordered at all. Glass x-ray spectrum looks like a big potato. 

X-ray diffraction patterns of diamond vs glass

The way physicists categorize crystals is with patterns called Bravais lattices. The Bravais lattice of diamond is cubic face centered, or CFC. If you want to get technical, a diamond is a CFC crystal with a motif of carbon atoms in positions (0, 0, 0) and (1/4, 1/4, 1/4). It looks like this:

Diamond Bravais lattice

"Diamonds are cool. Literally. They dissipate heat like crazy. In facts, your laptop would already be made of diamond if it wasn’t for the ridiculous price of such a thing." That's my friend Gabriel Antonius talking.

He really knows his stuff. We've done our PhDs together in condensed matter physics (the branch of physics that looks at crystals). He worked on fancy algorithms to simulate electrons in diamonds. 

He explains further : "Because carbon is such a light atom, it is constantly jiggling around, carrying heat through the material. But even if you were to cool down a diamond to the absolute zero, the atoms would still be vibrating. This is a quantum effect known as the zero-point motion, and it stems from the Heisenberg uncertainty principle. In a crystal, the uncertainty principle tells us that you cannot know simultaneously the position of the atoms and how much they vibrate. So while we know that the carbon atoms of diamond sit 1.5 Angstrom apart on average, there is always a 10% uncertainty on the position of each atom."

There you have it. The quantum mechanics of bling.

What Gabriel didn't tell you is that he's also a musician and a huge Pink Floyd fan. So I toyed with the idea of mixing Pink Floyd and condensed matter physics. The fusion of the song "Shine On You Crazy Diamond" and the crystal structure came together naturally in a moment of geekness.

I dedicate the "Shine on you crazy diamond" t-shirt design to Gabriel. You can have one, too.