Abstract
Recent theoretical and experimental studies have produced several unusual and interesting results on dense lithium, the first metal in the periodic table. These include the deviation from simple metal behaviour, superconductivity at 17 K, and a metal to semiconductor transition 1-5 . Despite these efforts, at present there is no agreement on the location of the high-pressure solid phases and melting curve of Li, and there is no clear picture of its phase diagram above 50 GPa (refs 4-7). Using powder and single-crystal high-pressure diffraction techniques, we have mapped out the lithium phase diagram up to 130 GPa over a wide temperature range between 77 and 300 K. Whereas the melting temperatures of materials usually rise under pressure, and even the lightest condensed gases, hydrogen and helium, melt at temperatures of the order of 10 3 K at 50 GPa (refs 8,9), we find that at these pressures lithium remains a liquid at temperatures as low as 190 K, by far the lowest melting temperature observed for any material at such pressure. We also find that in its solid state above 60 GPa, lithium adopts three novel and complex crystal structures not previously observed in any element. Estimates of the zero-point energy suggest that quantum effects play a significant role in shaping the lithium phase diagram.
Original language | English |
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Pages (from-to) | 211-214 |
Number of pages | 4 |
Journal | Nature Physics |
Volume | 7 |
Issue number | 3 |
DOIs | |
State | Published - Mar 2011 |
Externally published | Yes |
Funding
The authors are grateful to N. Ashcroft, A. Bergara and S. Bonev for very useful discussions. This work is supported by a research grant from the UK Engineering and Physical Sciences Research Council and facilities made available by the European Synchrotron Radiation Facility. Some of the single-crystal data were collected under ESRF LTP project HS-3090. APS is supported by DOE-BES, under Contract No. DE-AC02-06CH11357. HPCAT is supported by DOE-BES, DOE-NNSA and NSF. Work carried out at HPCAT was supported as part of the EFree initiative, funded by the US Department of Energy, Office of Science, under Award Number DE-SC0001057. O.D. acknowledges support from the Royal Society.