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Metal-Insulator Transition in Li and LiH Final Report.

DE200515008095

Publication Date	2002
Personal Author	Bastea, M.; Cauble, R. C.
Page Count	10
Abstract	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.
Keywords	Lithium Coupling(Interaction) Liquid lithium Electrical conductivity Electrons Atoms Lithium compounds Ionic pairing
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200520

Metal-Insulator Transition in Li and LiH Final Report.

Metal-Insulator Transition in Li and LiH Final Report.
DE200515008095

Publication Date	2002
Personal Author	Bastea, M.; Cauble, R. C.
Page Count	10
Abstract	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.
Keywords	Lithium Coupling(Interaction) Liquid lithium Electrical conductivity Electrons Atoms Lithium compounds Ionic pairing
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200520