2020/09/24 by Mary Anne White, Samer Kahwaji, Vera L.S. Freitas +6 · 1 citation
Earth and Planetary Sciences · Materials Science · Physics and Astronomy · #High-pressure geophysics and materials #Diamond and Carbon-based Materials Research #Advanced Chemical Physics Studies
paper · doi:10.1002/anie.202009897
openalex publication_date 2020/09/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Abstract Recent density‐functional theory (DFT) calculations raised the possibility that diamond could be degenerate with graphite at very low temperatures. Through high‐accuracy calorimetric experiments closing gaps in available data, we reinvestigate the relative thermodynamic stability of diamond and graphite. For T <400 K, graphite is always more stable than diamond at ambient pressure. At low temperatures, the stability is enthalpically driven, and entropy terms add to the stability at higher temperatures. We also carried out DFT calculations: B86bPBE‐25X‐XDM//B86bPBE‐XDM and PBE0‐XDM//PBE‐XDM results overlap with the experimental − T Δ S results and bracket the experimental values of Δ H and Δ G , displaced by only about 2× the experimental uncertainty. Revised values of the standard thermodynamic functions for diamond are Δ f H o =−2150±150 J mol −1 , Δ f S o =3.44±0.03 J K −1 mol −1 and Δ f G o =−3170±150 J mol −1 .