Charge carriers and electrical conductivity in fluid molecular dielectrics under wide pressure range

Fluid hydrogen, oxygen, and nitrogen at very high pressures and temperatures demonstrate high conductivity close to the so-called “minimum metal conductivity”. Electrophysical properties of these liquids in the semi-conducting transition region are practically unknown. In this work a simple model is used for estimating the bottom energy of the electron conduction band and the electron-forbidden gap energy. It is shown that electrons in liquid hydrogen, oxygen, and nitrogen are localized as molecular negative ions surrounded by voids about 0.3-0.5 nm in radius. The conductivity of these fluids at not very high pressures is connected to the transfer of positively charged clusters and negatively charged bubbles created around negative ions. As the pressure and density increase, molecular dissociation occurs and electron localization on atoms becomes more favorable, also with the creation of a void around atomic negative ions. At a sufficiently high concentration of atoms, the probability of the tunnel transition of an electron from one atom to another becomes close to unity, the energy level of the negative ion degenerates in the band, and the conductivity is caused by the transfer of these quasifree electrons. It is supposed that this charge transfer mechanism may play an important role in the dielectric-metal transition region.