Ice VII is a high-pressure phase of ice that forms at pressures of over 2 GPa (20,000 atmospheres) and temperatures below about 1300 K. It is a dense crystal structure with shorter hydrogen bonds compared to normal ice, resulting in a higher density. Ice VII has been studied primarily through laboratory experiments, using techniques such as diamond anvil cells to create extremely high pressures.

The existence of ice VII was first predicted by Linus Pauling in 1935, and it was later confirmed by experiments in the 1950s. It is one of many known crystalline phases of ice, each with its own unique structure and properties.

One interesting property of ice VII is that it is a good conductor of electricity under certain conditions. This makes it potentially useful for applications in high-pressure electronics and superconductivity research.

Ice VII is not found naturally on Earth's surface, as the pressures required for its formation are only found deep within the Earth or in extreme environments like outer space. However, it is believed to exist in large quantities in the ice mantles of distant icy moons and planets, such as Jupiter's moon Europa.

Overall, ice VII is a fascinating form of ice that exhibits unique properties under high pressure conditions. Its study not only helps us understand the behavior of water under extreme conditions but also has implications for fields such as geophysics and planetary science.