Phase diagrams and critical properties of (classical) Coulomb systems

Quantum electrodynamics (QED) is given as the underlying theory for describing matter composed of nuclei and electrons forming ions, atoms, and molecules. However, non-relativistic QED (moderate energies and velocities of particles) does not sufficiently describe the behavior of matter because QED cannot account for spin-dependent interactions such as magnetic dipole and magnetic moment interactions. QED is sufficient when nuclear charges, temperatures and densities are moderate, spin-dependent forces are weak, and particle-field interactions do not excite high-frequency electromagnetic fields. Models which neglect the latter two interactions and assume a two-body system approximation are Coulomb systems. To describe a three-dimensional Coulomb system in thermal equilibrium, the Coulomb potential must be regularized at short distances