Structural optimization at finite temperature based on anharmonic phonon theory*

We develop a theory of ab-initio structural optimization at finite temperature based on the self-consistent phonon (SCP) theory[1], which nonperturbatively considers the anharmonic effect. We implement the theory to the ALAMODE package[2,3], which is an open-source package of anharmonic phonon calculation. By applying our method, we successfully calculate the structural transition of BaTiO₃, a prototypical ferroelectric material. Our method makes it possible to efficiently compute the structure of materials at finite temperature in a deterministic way. We expect that the method is effective in investigating a wide range of materials with multiple competing structures.

[1] D. J. Hooton. Phil. Mag. 3.25 (1958)

[2] T. Tadano, S. Tsuneyuki PRB 92.054301 (2015)

[3] Y. Oba, et al. PRMat 3.033601 (2019)