Metal-Insulator Transition in Li and LiH - Final Report

Bastea, M. ; Cauble, R.

Lawrence Livermore National Laboratory

关键词: Compression;    Interstitials;    37 Inorganic, Organic, Physical And Analytical Chemistry;    36 Materials Science;    Atoms;   

DOI  :  10.2172/15008095
RP-ID  :  UCRL-ID-146792
RP-ID  :  W-7405-ENG-48
RP-ID  :  15008095

美国|英语

来源: UNT Digital Library

【 摘 要 】

The main goals of this project were the search for a predicted nonmetallic high-pressure phase of Li and finding the metallization conditions for LiH. It has been predicted by Neaton & Ashcroft at Cornell [1] that the lithium atoms would pair at pressures around 100 GPa and their valence electrons would become localized in the interstitial regions and therefore non-conducting. LiH, an ionic compound, provides the unique opportunity to understand the effects of coupling two elements with opposite tendencies at extreme conditions and to study fundamental principles such as metallization and pairing. We measured the electrical conductivity of liquid lithium at pressures up to 1.8 Mbar and 4-fold compression, achieved through shock reverberation experiments [2]. We found that the results were consistent with a departure of the electronic properties of lithium from the nearly free electron approximation at high pressures and with ionic pairing correlations in the Mbar regime. Given the expected small effect of the temperature on the conductivity at high densities, the apparent conductivity drop and the behavior of the ionic core at the highest pressures could be interpreted as a decrease of the overall volume available for the electrons. It may be interesting to see if the exclusionary effects mentioned above, that lead to a very non-uniform distribution of the valence electrons, translate into the analog of classical depletion forces [3], enhancing the ionic pairing correlations in a mixture, e.g. LiH. Higher temperatures would ultimately destroy pairing correlations in the liquid. Estimates of the temperatures required should be possible, but need to rely on more detailed calculations, that could be tested against the experimental results of this study.