2. Properties of solid materials at very high pressures

2.1 Introduction

In this section, we present the main effects of very high pressures on the properties of solid materials. Generally speaking, in this type of material, the effect of pressure reduces interatomic or molecular distances. This distance reduction can also be achieved by cooling the material. For many condensed materials, the coefficient of expansion per degree is approximately the same as the isothermal compressibility per bar (0.1 MPa) and is of opposite sign. However, the lattice continues to vibrate in pressurized materials, whereas when the material is cooled, the vibrations are frozen. Condensed phases thus differ from gaseous phases. When pressure is applied to a solid, complex variations in electronic structure and energies occur due to strong interactions between...