期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 60, 期 3, 页码 1546-1549出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.202009897
关键词
density-functional calculations; diamond; graphite; phase stability; thermodynamics
资金
- NSERC
- Dalhousie University through the Clean Technology Research Institute
- Government of Nova Scotia (Nova Scotia Graduate Scholarship)
- German Science Foundation (DFG) [VE 265-14/2]
- Government of Russian Federation [220, 14.Z50.31.0038]
- Fundacao para a Ciencia e Tecnologia (FCT) of Portugal [UIDB/00081/2020]
- FCT-I.P.
Recent studies using density-functional theory calculations and high-accuracy calorimetric experiments have revealed that graphite is more thermodynamically stable than diamond at ambient pressure, with stability being driven by enthalpy at low temperatures and entropy at higher temperatures. DFT calculations showed good agreement with experimental results, providing revised values for the standard thermodynamic functions of diamond.
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 T400 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 Delta S results and bracket the experimental values of Delta H and Delta G, displaced by only about 2x the experimental uncertainty. Revised values of the standard thermodynamic functions for diamond are Delta H-f(o)=-2150 +/- 150 J mol(-1), Delta S-f(o)=3.44 +/- 0.03 J K-1 mol(-1) and Delta(f)G(o)=-3170 +/- 150 J mol(-1).
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