  Under high pressure, krypton, one of the most inert elements is predicted to
become sufficiently reactive to form a new class of krypton compounds; krypton
oxides. Using modern ab-initio evolutionary algorithms in combination with
Density Functional Theory, we predict the existence of several
thermodynamically stable Kr/O species at elevated pressures. In particular, our
calculations indicate that at approx. 300 GPa the monoxide, KrO, should form
spontaneously and remain thermo- and dynamically stable with respect to
constituent elements and higher oxides. The monoxide is predicted to form
non-molecular crystals with short Kr-O contacts, typical for genuine chemical
bonds.
