Structural and physical properties of condensed H$-2$O systems up to 2 GPa: A brief review

The condensed H$_2$O systems at the pressure above 2 GPa are very different from common water. Since they may exist in the deep of some celestial bodies, the research on these H$_2$O systems are essential to the further discussion of the physical states, elements' distribution, geological evolutions and even the origins of these celestial bodies (including our earth). In addition, as the condensed H$_2$O system is one of the main detonation products, the research on it is also significant to the development of the higher performance explosives. As a result, the condensed H$_2$O systems have been extensively studied by several theoretical and experimental methods in recent decades. Many achievements about the systems have been obtained in the last decades, but there are still some open questions. A brief review of the achievements of the structural and physical properties of the condensed H$_2$O systems up to 2 GPa is included in this paper, as well as some open questions about them are also presented herein.