Structure and vibrations in rare-earth nickelates with nonempirical extended Hubbard functionals

Transition-metal oxide represent one of the most interesting classes of materials in condensed matter physics. Notable representatives are the
rare-earth nickelates RNiO3 (R = lanthanide), that exhibit a metal-insulator transition in which a strong interplay between electronic, structural and magnetic degrees of freedom takes place. In particular, a strong oxygen isotope effect was observed for R = Pr, Nd [1]. Motivated by these findings, we study the vibrational properties of the low-temperature phase of the praseodymium nickelate using extended (DFT+U+V) Hubbard functionals, to get more insight on the coupling between the structural and electronic degrees of freedom at the transition. Since also the Hubbard parameter are calculated from first principles [2], the approach is fully nonempirical.
[1] M. Medarde, P. Lacorre, K. Conder, F. Fauth, and A. Furrer, Phys. Rev. Lett. 80, 2397 (1998).
[2] Iurii Timrov, Nicola Marzari, and Matteo Cococcioni, Phys. Rev. B 98, 085127 (2018).