A Divalent Fluid Metal

Mercury has the lowest known critical temperature (1478 °C) of any fluid metal. It is therefore particularly attractive to experimentalists. Mercury is also considerably less corrosive than many metals, especially the alkali metals discussed in the preceding chapter. These relatively favorable circumstances permit precise measurement of the electrical, optical, magnetic, and thermophysical properties of fluid mercury. With care, one can control temperatures accurately enough to determine the asymptotic behavior of physical properties as the liquid-vapor critical point is approached. Such truly critical data are especially valuable for exploring the relationship between the liquid-vapor and MNM transitions. Of the expanded metals exhibiting MNM transitions, mercury is therefore the most extensively investigated. It is the only expanded divalent metal whose critical region has proven to be experimentally accessible. 

If the separation between s- and p-bands is not too large, we can expect the band tails to overlap in the region of the Fermi energy. In this case, the energy gap of the crystal would be replaced by a pseudogap  

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