How does water ice change structure as pressure increases?

As pressure increases, water ice undergoes structural transformations to achieve denser, more closely packed atomic arrangements. Like other molecular solids, water ice (H₂O) experiences a series of structural phase transitions when subjected to high pressure, resulting in successively denser configurations of its molecular units.1

At standard atmospheric pressure, ice typically forms an open hexagonal lattice. However, as pressure rises, the material is forced into more efficient packing structures to accommodate the increased external force. These transitions are part of a broader physical phenomenon where materials undergo structural changes to minimize volume under high-pressure conditions.231