Lattice dynamics of palladium in the presence of electronic correlations

We compute the phonon dispersion, density of states, and the Grüneisen parameters of bulk palladium in the combined density functional theory (DFT) and dynamical mean-field theory. We find good agreement with experimental results for ground-state properties (equilibrium lattice parameter and bulk modulus) and the experimentally measured phonon spectra. We demonstrate that at temperatures Tâ‰20K the phonon frequency in the vicinity of the Kohn anomaly, ωT1(qK), strongly decreases. This is in contrast to DFT where this frequency remains essentially constant in the whole temperature range. Apparently, correlation effects reduce the restoring force of the ionic displacements at low temperatures, leading to a mode softening. © 2020 American Physical Society.We are grateful to Ferdi Aryasetiawan, Milos Radonjić, and Weiwei Sun for stimulating discussions. W.H.A. thanks Levente Vitos for the kind hospitality at KTH Stockholm. I.D.M. acknowledges support by the appointment to the JRG program at the APCTP through the Science and Technology Promotion Fund and Lottery Fund of the Korean Government, as well as support by the Korean Local Governments, Gyeongsangbuk-do Province, and Pohang City. Part of the computations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at Beskow. Financial support offered by the Augsburg Center for Innovative Technologies, and by the Deutsche Forschungsgemeinschaft (through TRR 80/F6) is gratefully acknowledged. I.L. acknowledges support by the state assignment of Minobrnauki of Russia (theme “Electron” No. AAAA-A18-118020190098-5)