Reinhardt Aleks, Bethkenhagen Mandy, Coppari Federica, Millot Marius, Hamel Sebastien, Cheng Bingqing
Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
École Normale Supérieure de Lyon, Université Lyon 1, Laboratoire de Géologie de Lyon, CNRS UMR 5276, 69364, Lyon Cedex 07, France.
Nat Commun. 2022 Aug 10;13(1):4707. doi: 10.1038/s41467-022-32374-1.
Most experimentally known high-pressure ice phases have a body-centred cubic (bcc) oxygen lattice. Our large-scale molecular-dynamics simulations with a machine-learning potential indicate that, amongst these bcc ice phases, ices VII, VII' and X are the same thermodynamic phase under different conditions, whereas superionic ice VII″ has a first-order phase boundary with ice VII'. Moreover, at about 300 GPa, the transformation between ice X and the Pbcm phase has a sharp structural change but no apparent activation barrier, whilst at higher pressures the barrier gradually increases. Our study thus clarifies the phase behaviour of the high-pressure ices and reveals peculiar solid-solid transition mechanisms not known in other systems.
大多数实验已知的高压冰相具有体心立方（bcc）氧晶格。我们利用机器学习势进行的大规模分子动力学模拟表明，在这些bcc冰相中，冰VII、VII'和X在不同条件下是同一热力学相，而超离子冰VII″与冰VII'有一个一级相界。此外，在约300 GPa时，冰X与Pbcm相之间的转变有急剧的结构变化但没有明显的活化能垒，而在更高压力下该能垒逐渐增加。我们的研究因此阐明了高压冰的相行为，并揭示了其他系统中未知的特殊固-固转变机制。
