期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：24
页码：13374-13378
DOI：10.1073/pnas.2001128117
出版社：The National Academy of Sciences of the United States of America
摘要：Molecular hydrogen forms the archetypical quantum solid. Its quantum nature is revealed by behavior which is classically impossible and by very strong isotope effects. Isotope effects between H 2 , D 2 , and HD molecules come from mass difference and the different quantum exchange effects: fermionic H 2 molecules have antisymmetric wavefunctions, while bosonic D 2 molecules have symmetric wavefunctions, and HD molecules have no exchange symmetry. To investigate how the phase diagram depends on quantum-nuclear effects, we use high-pressure and low-temperature in situ Raman spectroscopy to map out the phase diagrams of H 2 –HD– D 2 with various isotope concentrations over a wide pressure–temperature ( P - T ) range. We find that mixtures of H 2 , HD, and D 2 behave as an isotopic molecular alloy (ideal solution) and exhibit symmetry-breaking phase transitions between phases I and II and phase III. Surprisingly, all transitions occur at higher pressures for the alloys than either pure H 2 or D 2 . This runs counter to any quantum effects based on isotope mass but can be explained by quantum trapping of high-kinetic energy states by the exchange interaction.
