Hydrogen and lithium,along with their compounds,are crucial materials for nuclear fusion research.High-pressure studies have revealed intricate structural transitions in all these materials.However,research on lithium...Hydrogen and lithium,along with their compounds,are crucial materials for nuclear fusion research.High-pressure studies have revealed intricate structural transitions in all these materials.However,research on lithium hydrides beyond LiH has mostly focused on the low-temperature regime.Here,we use density functional theory and ab initio molecular dynamics simulations to investigate the behavior of LiH_(2),a hydrogen-rich compound,near its melting point.Our study is particularly relevant to the low-pressure region of the compression pathway of lithium hydrides toward fusion.We discovered a premelting superionic phase transition in LiH_(2)that has significant implications for its mass transportation,elastic properties,and sound velocity.The theoretical boundary for the superionic transition and melting temperature was then determined.In contrast,we also found that the primary compound of lithium hydrides,LiH,does not exhibit a superionic transition.These findings have important implications for optimizing the compression path to achieve the ignition condition in inertial confinement fusion research,especially when lithium tritium-deuteride(LiTD)is used as the fuel.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFB3802300)the National Natural Science Foundation of China(Grant No.11672274)the NSAF(Grant No.U1730248)。
文摘Hydrogen and lithium,along with their compounds,are crucial materials for nuclear fusion research.High-pressure studies have revealed intricate structural transitions in all these materials.However,research on lithium hydrides beyond LiH has mostly focused on the low-temperature regime.Here,we use density functional theory and ab initio molecular dynamics simulations to investigate the behavior of LiH_(2),a hydrogen-rich compound,near its melting point.Our study is particularly relevant to the low-pressure region of the compression pathway of lithium hydrides toward fusion.We discovered a premelting superionic phase transition in LiH_(2)that has significant implications for its mass transportation,elastic properties,and sound velocity.The theoretical boundary for the superionic transition and melting temperature was then determined.In contrast,we also found that the primary compound of lithium hydrides,LiH,does not exhibit a superionic transition.These findings have important implications for optimizing the compression path to achieve the ignition condition in inertial confinement fusion research,especially when lithium tritium-deuteride(LiTD)is used as the fuel.
