High-pressure-high-temperature equation of state of KCl and KBr.

The equation of state of KCl and KBr, compressed in a helium pressure medium in a diamond-anvil cell, has been measured by x-ray diffraction in the Bl and B2 phases up to 165 GPaat 298 K. The P-V-T of B2 KCl and B2 KBr has been calculated by ab initio molecular dynamics in a wide compression range and up to 7000 K. The thermal pressure exhibits a linear behavior with temperature and remains low under high compression. The experimental P-V points and the thermal pressure calculated by molecular dynamics have been used to set up a high-pressure-high-temperature equation of state of B2 KCl and B2 KBr. With these equations of state, B2 KCl and B2 KBr can be used as pressure markers in laser-heated diamond-anvil-cell experiments. [ABSTRACT FROM AUTHOR]