How does high pressure change the physical and chemical properties of matter?

High pressure fundamentally alters matter by reducing volume and shortening mean interatomic distances, which directly impacts chemical bonding and internal energy. Unlike temperature, which influences kinetic energy, pressure forces atoms closer together, serving as a powerful probe of atomic interactions.12

Physical and Structural Effects

Under high pressure, materials often undergo phase transitions to denser, more closely packed atomic arrangements. For example, gases can be forced into solid states, and minerals may undergo structural rearrangements that increase the coordination number of atoms. A notable phenomenon is metallization; as pressure forces the overlap of electron orbitals, insulators can transform into metals, a process documented in elements like silicon, oxygen, and hydrogen.3

Material Properties

High-pressure research, pioneered by Percy Williams Bridgman, has shown that pressure induces both continuous and discontinuous changes in properties such as electric conductivity, thermal conductivity, and viscosity. While many properties vary smoothly, some materials exhibit sharp, reproducible discontinuities at specific pressures, signaling structural shifts. These effects are critical for synthesizing superhard materials and understanding the composition of planetary interiors.12