Bulk hexagonal diamond
TL;DR
You probably know that diamonds are made of carbon atoms arranged in a specific pattern—like a perfectly stacked 3D grid. But imagine if those same carbon atoms could be stacked in a slightly different pattern, like a honeycomb, instead of a cube. Scientists have long believed this 'hexagonal diamond' exists because they found hints of it in rocks from meteorite impact sites, suggesting the extreme heat and pressure of a space rock smashing into Earth could create it. But nobody could make it in the lab or prove it was real on its own—until now. These researchers took a special form of super-flat graphite (the stuff in pencils), squeezed it really hard in just the right direction while heating it up, and successfully made millimeter-sized chunks of hexagonal diamond. They confirmed it's real, it's slightly harder than regular diamond, and it holds up to heat really well. Think of it as discovering a new flavor of the hardest material on Earth.
Known as the 'ultimate semiconductor', cubic diamond (CD) has gained substantial interest both scientifically and industrially. Its polymorph, hexagonal diamond (HD), is even more intriguing because of its fascinating properties associated with the meteorite impacts. As no solid experimental evidence has been provided to prove its existence, the physical properties of HD remain largely unexplored. Here we report the synthesis of millimetre-sized, phase-pure HD from highly oriented pyrolytic graphite (HOPG) compressed along the c-axis at elevated temperatures. Combining advanced structural characterizations and theoretical simulations, we confirm the identity of HD and clarify the transformation pathway from graphite. Bulk HD exhibits a slightly higher hardness than CD and high thermal stability. These findings resolve the long-standing controversy on the existence of HD as a discrete carbon phase and provide new insight into the graphite-to-diamond phase transition, paving the way for future research and practical use of HD in advanced technological applications.
- 1Synthesis of millimetre-sized, phase-pure hexagonal diamond (HD) from highly oriented pyrolytic graphite (HOPG) compressed along the c-axis at elevated temperatures
- 2Advanced structural characterizations and theoretical simulations confirm the identity of HD and clarify the transformation pathway from graphite
- 3Bulk HD exhibits a slightly higher hardness than cubic diamond (CD) and high thermal stability
- 4The findings resolve the long-standing controversy on the existence of HD as a discrete carbon phase
- 5New insight provided into the graphite-to-diamond phase transition, opening avenues for practical use of HD in advanced technological applications
Over 20,000 precolonial earthworks in the Southwest Amazonia
Imagine flying a special laser scanner over the Amazon jungle that can 'see through' the treetops, like X-ray vision for the ground. When scientists did this, they found over 20,000 geometric shapes — ditches, mounds, and enclosures — built by ancient people long before Europeans arrived. These aren't small things: they're massive earthen structures, like monuments. This means the Amazon rainforest, which most people picture as empty wilderness, was actually home to millions of people who built cities and shaped the landscape. Think of it like discovering that a forest you thought was wild was actually someone's ancient garden on a continental scale.
A digitally controlled silicon quantum processing unit
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The 2026 World Cup's grass is an engineering problem
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Remarks on the disproof of the unit distance conjecture
Imagine you scatter a bunch of dots on a piece of paper. The question is: how many pairs of those dots can be exactly 1 inch apart? The Erdős unit distance conjecture asked whether there's a specific mathematical formula that limits how often this can happen as you add more and more dots. Think of it like asking how many friendships can exist in a town where friends are defined as people who live exactly one mile apart — there's a suspected maximum, and Erdős guessed what that maximum should be. For decades, no one could prove or disprove his guess. Now, an AI apparently found a specific arrangement of dots (a 'counterexample') that breaks the expected limit, proving Erdős's conjecture was wrong. A team of elite mathematicians then checked and explained the AI's work in this paper.