Harder Than Diamond? The New Hexagonal Diamond Breakthrough (EP 38)

Hosted by Lester Nare and Krishna Choudhary, this episode is a deep dive into one of the strangest and most hard-fought materials science stories in decades: the claim that researchers have finally synthesized bulk hexagonal diamond, also known as lonsdaleite. They break down why this material matters, how it differs from ordinary cubic diamond, why scientists argued about its existence for more than 50 years, and what the new Nature paper actually did to convince skeptical reviewers.

Summary

Why hexagonal diamond matters — if real, it is a long-sought carbon phase that could be slightly harder than conventional diamond and useful in extreme industrial settings.

The first-principles chemistry — carbon allotropes, x-ray crystallography, cubic diamond, and the ABAB stacking that makes hexagonal diamond different.

The experimental breakthrough — how the new team engineered around the default pathway to ordinary diamond by controlling graphite orientation and pressure direction.

The controversy — why the peer review was intense, and how the new paper relates to an earlier 2025 Nature paper with a similar claim.

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