Why can pure water remain liquid at pressures below atmospheric pressure?

Pure water can remain in a liquid state at pressures below atmospheric pressure—and even at negative pressures—because of the strong attractive forces between its molecules. In a liquid, these molecules are held together by short-range cohesive forces, and work must be performed to break these links to form a gas phase.1

In a sample of very pure water, the liquid can withstand significant "stretching" or tension, meaning it can exist at negative pressures (well below $-{10}^7$ newtons per square metre) before it ruptures and vaporizes. This stability is maintained as long as there are no suitable nuclei—such as suspended dust particles, dissolved gases, or sharp surface irregularities—that allow for the formation of vapour-filled cavities.12

When such nuclei are present, the process of cavitation occurs, where the liquid reaches its vapour pressure and forms bubbles, causing the liquid to transition into a gas. In practical applications, such as with marine propellers or pumps, this phenomenon is often triggered by high-velocity flow, which reduces the local pressure and leads to the formation and subsequent collapse of these vapour cavities.314