Ab Initio Thermochemistry of Solid‐State Materials

Abstract

In this contribution we introduce an electronic-structure-theory-based approach to a quantum-chemical thermochemistry of solids. We first deal with local and collective atomic displacements and explain how to calculate these. The fundamental importance of the phonons, their dispersion relations, their experimental determination as well as their calculation is elucidated, followed by the systematic construction of the thermodynamic potentials on this basis. Subsequently, we provide an introduction for practical computation as well as a critical analysis of the level of accuracy obtainable. We then show how different solid-state chemistry problems can be solved using this approach. Among these are the calculation of activation energies in perovskite-like oxides, but we also consider the use of theoretical vibrational frequencies for determining crystal structures. The pressure and temperature polymorphism of elemental tin which has often been classically described is also treated, and we energetically classify the metastable oxynitrides of tantalum. We also demonstrate, using the case of high-temperature superconductors, that such calculations may be used for an independent evaluation of thermochemical data of unsatisfactory accuracy. Finally, we show the present limits and the future challenges of the theory.

Synthesis and Crystal Structure of δ-TaON, a Metastable Polymorph of Tantalum Oxide Nitride

“…With a combination of its eigenvalues (phonon frequencies) with Bose-Einstein statistics, the free phonon energy was obtained. 24 Thermodynamic properties at finite temperatures are straightforwardly accessible from these data.…”

Phase stabilities at a glance: Stability diagrams of nickel dipnictides

“…4 Dronskowski a) Author to whom correspondence should be addressed. Electronic mail: richard.weihrich@chemie.uni-r.de et al published a state-of-the-art contribution on ab initio thermochemistry of solid-state materials 5 and they developed energy-volume diagrams for systems with a fixed stoichiometry including a multitude of possible structure types. 6 The concept was applied by our group to calculate the relative stability of black and red phosphorus and arsenic.…”

A density-functional theory approach to the existence and stability of molybdenum and tungsten sesquioxide polymorphs

“…Phonon frequencies and eigenvectors were calculated from the dynamical matrices. The pDOS can then be assessed by summing up over all phonon frequencies [13].…”