Origin of the transition entropy in vanadium dioxide

Thomas A. Mellan, Hao Wang, Udo Schwingenschlögl, Ricardo Grau-Crespo

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15 Scopus citations

Abstract

The reversible metal-insulator transition in VO2 at Tc≈340 K has been closely scrutinized yet its thermodynamic origin remains ambiguous. We discuss the origin of the transition entropy by calculating the electron and phonon contributions at Tc using density functional theory. The vibration frequencies are obtained from harmonic phonon calculations, with the soft modes that are imaginary at zero temperature renormalized to real values at Tc using experimental information from diffuse x-ray scattering at high-symmetry wave vectors. Gaussian process regression is used to infer the transformed frequencies for wave vectors across the whole Brillouin zone, and in turn compute the finite temperature phonon partition function to predict transition thermodynamics. Using this method, we predict the phase transition in VO2 is driven 5 to 1 by phonon entropy over electronic entropy, and predict a total transition entropy that agrees (within 5%) with the calorimetric value.
Original languageEnglish (US)
JournalPhysical Review B
Volume99
Issue number6
DOIs
StatePublished - Feb 26 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: R.G.-C. and T.A.M. acknowledge funding from the UK's Engineering and Physical Sciences Research Council EPSRC (Grant No. EP/J001775/1). Via the UK's HPC Materials Chemistry Consortium, which is funded by EPSRC (Grant No. EP/L000202), this work made use of ARCHER, the UK's national high-performance computing services. The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST). T.A.M. is grateful for computational support from the UK Materials and Molecular Modelling Hub, which is partially funded by EPSRC (Grant No. EP/P020194), for which access was obtained via the UKCP consortium and funded by EPSRC Grant No. EP/P022561/1.

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