Stability of dynamically disordered materials from ab initio molecular dynamics

Large atomic displacements and atoms vibrating without well-defined equilibrium positions are the signatures of dynamically disordered materials. These materials show immense potential in applications, such as superionic conductors, solid-state batteries, and fuel cells. The biggest obstacle in living up to this potential is the limited stability of the dynamically disordered phases. To predict it the free energies has to be calculated. That has long been a challenge. We have introduced a method that offers a solution [1]. It relies on a density functional theory (DFT), ab initio molecular dynamics (AIMD), and stress-strain thermodynamic integration between the dynamically disordered phase and its metastable ordered variant. The successful application of the method to the stability of notorious cubic bismuth oxide and lithium carbide [2] will be discussed.

[1] J. Klarbring and S. I. Simak, Phys. Rev. Lett. 121, 225702 (2018).
[2] S. Filippov, J. Klarbring, U. Häussermann, and S. I. Simak, Phys. Rev. Mater. 3, 023602 (2019).