Thermochemistry, energetic modelling and systematic
Experimental thermochemistry provides data on heat capacities, entropies, enthalpies of phase transitions, and enthalpies of formation of minerals and other materials relevant to the Earth Sciences. Such data can be used to construct empirical models of systematic trends and to benchmark models and first principles calculations. This paper provides a summary of the capabilities of modern experimental techniques and focuses on three case studies (lanthanide and actinide oxide materials, perovskites and nanomaterials) which link calorimetric data and computational predictions.
Thermodynamics plays a twofold role in the science of minerals and materials. At the macroscopic level, thermodynamic parameters provide a description of the equilibrium state of complex multicomponent systems, enabling the calculation of crystallisation and melting relations, aqueous solubility, ordering, exsolution, solid solution formation, phase transformation and other processes relevant to the evolution of phase chemistry with composition, pressure, temperature and, in some cases, time. On the microscopic level, energetics provide insight into the strengths of chemical bonds, the nature of lattice vibrations and processes involving the ordering of atoms, electrons and spins. In the latter sense, thermodynamics can be viewed as a crude form of spectroscopy, smeared out over the frequency domain, and coming out with values of energy, heat capacity and entropy which reflect the most important interatomic interactions, averaged by nature. This averaging is the strength of thermodynamics; it assesses the net effect of many competing interactions. The real thermodynamic parameter, when correctly measured, provides a comparison and benchmark for theory, which uses, of necessity, simplified models of interatomic interactions, whether by using