Mechanical instability in ice I h. A mechanism for pressure-induced amorphization

The phenomenon of pressure-induced crystalline →amorphous phase transformation in ice Ih has been studied with constant-pressure molecular dynamics calculations. It was found that although the temperature dependency of the transformation pressure resembles that of the extrapolated melting curve, the actual mechanism is due to a mechanical instability in the water framework. The elastic moduli calculated at the transition show a violation of Born criteria for mechanical stability.