H2O: another ice phase and its melting curve

The large disagreement in the previously measured melting curves of H2O above 20GPa may be explained by new measurements in the laser-heated diamond cell, revealing a transition from ice VII to a new solid phase. This transition was most likely interpreted as melting in previous melting experiments due to the observed loss of Raman or X-ray signals. The structure of this new phase will therefore be difficult to indentify.