Electrical conductivity and equations of states of $\beta$-rhombohedral boron in the megabar dynamic pressure range

The pressure dependence of the conductivity of boron under conditions of a stepwise shock compression of megabaric range is studied. With this purpose, the following problems have been solved. The conductivity of boron has been measured in the range of dynamic pressures, where boron has different high-pressure phases. The equations of state of $\beta$-rhombohedral and amorphous boron have been constructed in a megabaric pressure range. The thermodynamic states of boron in the conditions of these experiments are calculated, which, in combination with the measurement data, made it possible to determine the change in the boron conductivity in the conditions of strong stepwise shock compression at dynamic pressures to 110 GPa. The increase in the conductivity of polycrystalline boron at megabar pressures is interpreted as a result of a nonmetal–metal transition.