Temperature-Dependent Anharmonic Phonons in Quantum Paraelectric KTaO<sub>3</sub> by First Principles and Machine-Learned Force Fields
- Author(s)
- Luigi Ranalli, Carla Verdi, Lorenzo Monacelli, Georg Kresse, Matteo Calandra, Cesare Franchini
- Abstract
Understanding collective phenomena in quantum materials from first principles is a promising route toward engineering materials properties and designing new functionalities. This work examines the quantum paraelectric state, an elusive state of matter characterized by the smooth saturation of the ferroelectric instability at low temperature due to quantum fluctuations associated with anharmonic phonon effects. The temperature-dependent evolution of the soft ferroelectric phonon mode in the quantum paraelectric KTaO3 in the range 0–300 K is modeled by combining density functional theory (DFT) calculations with the stochastic self-consistent harmonic approximation assisted by an on-the-fly machine-learned force field. The calculated data show that including anharmonic terms is essential to stabilize the spurious imaginary ferroelectric phonon predicted by DFT in the harmonic approximation, in agreement with experiments. Augmenting the DFT workflow with machine-learned force fields allows for efficient stochastic sampling of the configuration space using large supercells in a wide temperature range, inaccessible to conventional ab initio protocols. This work proposes a robust computational workflow capable of accounting for collective behaviors involving different degrees of freedom and occurring at large time/length scales, paving the way for precise modeling and control of quantum effects in materials.
- Organisation(s)
- Computational Materials Physics
- External organisation(s)
- Università degli Studi di Trento, University of Bologna, Sapienza University of Rome
- Journal
- Advanced Quantum Technologies
- Volume
- 6
- No. of pages
- 7
- ISSN
- 2511-9044
- DOI
- https://doi.org/10.1002/qute.202200131
- Publication date
- 02-2023
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103018 Materials physics, 102019 Machine learning
- Keywords
- ASJC Scopus subject areas
- Statistical and Nonlinear Physics, Electronic, Optical and Magnetic Materials, Nuclear and High Energy Physics, Mathematical Physics, Condensed Matter Physics, Computational Theory and Mathematics, Electrical and Electronic Engineering
- Portal url
- https://ucris.univie.ac.at/portal/en/publications/temperaturedependent-anharmonic-phonons-in-quantum-paraelectric-ktao3-by-first-principles-and-machinelearned-force-fields(0c568e95-99d2-43ad-96a1-d6bddcc32676).html