The Relative Thermodynamic Stability of Diamond and Graphite. (9th November 2020)

• Record Type: Journal Article
• Authors: White, Mary Anne; Kahwaji, Samer; Freitas, Vera L. S.; Siewert, Riko; Weatherby, Joseph A.; Ribeiro da Silva, Maria D. M. C.; Verevkin, Sergey P.; Johnson, Erin R.; Zwanziger, Josef W.
• Is Part Of: Angewandte Chemie. Volume 133:Number 3(2021)
• Page Start: 1570
• Page End: 1573
• Publication Date: 2020-11-09
• Subjects: density-functional calculations -- diamond -- graphite -- phase stability -- thermodynamics; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202009897
• Languages: English
• ISSNs: 0044-8249

Abstract

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 Δf H o =−2150±150 J mol −1, Δf S o =3.44±0.03 J K −1 mol −1 and Δf G o =−3170±150 J mol −1 . Abstract : Through experimental thermodynamics and density‐functional theory, it is shown that graphite is more stable than diamond for T <400 K.