Electronic structure of matter at high compression: Isostructural transitions and approach of the Fermi-gas limit

The paper is concerned with the effect of atomic-shell structure on the cold pressure of highly compressed matter up to 1 bar and above. The method is to compare band-structure calculations based on augmented spherical waves with results of the quantum statistical model. Elements treated explicitly are Li, He, Be, Al, and K. An oscillatory behaviour of cold pressure curves is systematically obtained due to isostructural electronic transitions. They are traced back to pressure-induced band shifts and electronic redistribution from bands of low angular momentum to bands of higher angular momentum. The shifts are shown to occur generally when squeezing normal matter with extended atoms into highly degenerate matter. (IFT)