Compression of CsCl and CsBr in the megabar range

The quasi-hydrostatic compression of cesium chloride and cesium bromide has been measured with X-ray diffraction up to 141 GPa at 300 K. A cubic to orthorhombictransition, with a >= 10% distortion of lattice parameters, is evidenced in CsBr around 60 GPa. A smaller distortion (similar to 1.5%) appears in CsCl at the same pressure, followed by a likely transition to a lower symmetry phase which starts at 134 GPa.P-Vcompression curves yield equation of state parameters in line with those of other B2 alkali halides.