Abstract

We formulate a first-principle scheme for structural optimization at finite temperature ($T$) based on the self-consistent phonon (SCP) theory, which accurately takes into account the effect of strong phonon anharmonicity. The $T$ dependence of the shape of the unit cell and internal atomic configuration is determined by minimizing the variational free energy in the SCP theory. At each optimization step, the interatomic force constants in the new structure are calculated without running additional electronic structure calculations, which makes the method dramatically efficient. We demonstrate that the thermal expansion of silicon and the three-step structural phase transitions in ${\mathrm{BaTiO}}_{3}$ and its pressure-temperature ($p\text{\ensuremath{-}}T$) phase diagram are successfully reproduced. The present formalism will open the way to the nonempirical prediction of physical properties at finite $T$ of materials having a complex structural phase diagram.

Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call