Research On Equation Of State And Conductivity Of Lithium Hydride Under High Pressure

Lithium hydride (LiH) and together with its isotopes is one of important thermo nuclear materials and also is a potential energetic materials in the future. It has the simplest electronic structure among ionic crystals, so the theoretical treatment is relatively easy compared with other materials. Therefore, its high-pressure behaviors have been the subject of theoretical and experimental studies. However, most previous theoretical results on equation of state (EOS) are not in agreement with the latest experimental data. In literatures EOS data of LiH are mainly from static high pressure measurement, but data from shock compression are less published. Especially, the experimental studies in shock-induced optical radiation, shock temperature and electrical conductivity of LiH under shock compression are not available. Our work includes three parts as follow:A many-body correlation compression model with clear physical picture is constructed. It is found to be reliable for calculating EOS of LiH, and it takes advantage over other models in treating exchange interaction among ions. The calculated isothermal equation of state is in good agreement with the latest static high pressure experimental data in the range of 0～90GPa. It indicates that our model correctly reflects the interactions among ions in LiH crystal under high pressure, and provides an effective theoretical tool for further experimental study under higher pressure;We measured the radiant characteristics of a LiH sample with porosity of 97%, and calculated its shock temperature. The experiments are conducted by means of two-stage light gas gun. The measured color temperature of the radiation is much higher than the predicted one by a uniform model. The discrepancy is attributed to the emission of the defects or local melt regions generated by shock wave;We measured the resistivity of the same kind of samples during shock compression. It is found that the shocked LiH samples have resistivity in the order of 10~2→10~1Ω·cm in the range of 35-87GPa, which is at the same level of so-called semiconductors. The mechanism of such a high conductivity is not clear now. We think our data are useful to investigate its structure phase transition, insulator-metal phase transition, their reversibility and electric conduction mechanism etc.