Structural distortion and electronic properties of NiO under high pressure: an abinitio GGA+U study

Abstract

The structural distortion and electronic properties of NiO under high pressureare investigated by means of first-principles calculations within the densityfunctional theory (DFT) in the generalized gradient approximation (GGA).The strong electronic correlations are also taken into account in the form ofGGA+U. Recent experiments implied that previous local density approximation (LDA) calculationsincorrectly predicted structural distortion under high pressure, especially above 60 GPa.The present results show that even GGA calculations do not give a proper description ofstructural distortion under high pressure, although much improved structural and bulkproperties are obtained. When strong correlations are included, overall agreement of thestructural distortions of NiO under high pressure is obtained. The lattice constantsa andc as well as theaxial ratio c/a are in good agreement with experiment over the entire experimentalpressure range. The successful prediction of the structural distortion ofGGA+U can be attributed to the reasonable description of nearest-neighbour magnetic exchangeinteractions. In addition, we also analyse the density of states under different pressures.Present results indicate that, with increasing pressure, the bandwidth increases and thebandgap transits from being a mixture of charge-transfer and Mott–Hubbard type towardssolely Mott–Hubbard type.