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arXiv · 2307.06291

Lattice dynamics related properties of Nickel: A comparative DFT and DFT+U study

Shivani Bhardwaj·Sudhir K. Pandey
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Abstract

The simultaneous influence of electronic correlations and magnetic ordering on the theoretical estimation of phonons and related properties of Ni is investigated. The work includes a comparative DFT and DFT+U study, where on-site Coulomb interaction parameter for 3$d$ electrons, $U$($U_{full}$)= 0.516 eV obatined from constarined random phase approximation (cRPA) calculations, is considered for DFT+U calculations. The analysis of phonon frequency estimates along high symmetric k-directions and sampled full-BZ (Brillouin zone) using Frozen phonon displacement method suggests the importance of both on-site Coulomb correlations and magnetism to account for the experimental frequencies. Further, prominent role of both the aspects is observed in the derived thermodynamic properties - Free-energy, specific heat \& entropy, within quasi-harmonic approximation (QHA) specially at high temperatures. The temperature dependent evaluation of thermal expansion coefficient($α$) and phonon density of states is performed together with the equilibrium elastic constants. The results obtained for Ni, suggest the significance of electronic energy correction due to both on-site Coulomb correlations and magnetic phase incorporation, to account for realistic description of experimental findings. This study realizes the inevitable role of correlation effects in studying the phononic properties of a correlated transition metal, hence directing a way to explore various other correlated electron systems for their lattice dynamics.

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Shivani Bhardwaj, Sudhir K. Pandey. 2023-07-12. Lattice dynamics related properties of Nickel: A comparative DFT and DFT+U study. https://arxiv.org/abs/2307.06291

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