Determining Hubbard U of VO2 by the quasi-harmonic approximation

Abstract

Vanadium dioxide VO2 is a strongly correlated material that undergoes a metal-to-insulator transition around 340 K. In order to describe the electron correlation effects in VO2, the DFT +U method is commonly employed in calculations. However, the choice of the Hubbard U parameter has been a subject of debate and its value has been reported over a wide range. In this paper, taking focus on the phase transition behavior of VO2, the Hubbard U parameter for vanadium oxide is determined by using the quasi-harmonic approximation (QHA). First-principles calculations demonstrate that the phase transition temperature can be modulated by varying the U values. The phase transition temperature can be well reproduced by the calculations using the Perdew–Burke–Ernzerhof functional combined with the U parameter of 1.5 eV. Additionally, the calculated band structure, insulating or metallic properties, and phonon dispersion with this U value are in line with experimental observations. By employing the QHA to determine the Hubbard U parameter, this study provides valuable insights into the phase transition behavior of VO2. The findings highlight the importance of electron correlation effects in accurately describing the properties of this material. The agreement between the calculated results and experimental observations further validates the chosen U value and supports the use of the DFT + U method in studying VO2.