3. Solid mechanical strength

3.1 Measuring a solid's resistance to volume change

The incompressibility modulus measures the resistance to volume change in solids, and thus provides an estimate of a material's elastic response to external hydrodynamic pressure. Note that this is outside the thermodynamic realm of phase transitions, which involve a change in the spatial arrangement of atoms or groups of atoms in the crystal lattice. In fact, a phase transition involves a reorganization of the electronic structure (through a change in symmetry, for example) which modifies the overall properties to a greater or lesser extent. However, as we approach the phase transition limit, we can artificially "freeze" a crystalline structure in its current state and impose volume.

The value of the incompressibility...