Electronic and Optical Properties of Sodium Niobate: A Density Functional Theory Study

Table 4

Structural properties of the rhombohedral phase of NaNbO₃.

	PBE	PBEsol	AM05	Experiment
a (Å)	5.556	5.489	5.506	5.481 [10]
c (Å)	13.888	13.720	13.762	13.685 [10]
(Å^3)	371.274	357.990	361.314	356.060 [10]
(GPa)	100.8	114.9	107.9	—
(GPa)	6.8	10.2	6.9	—
(eV)	2.819	2.660	2.709	—
	−120	−111	−100	—

Given are the lattice parameters a and c, the equilibrium unit-cell volume , the bulk modulus and its pressure derivative , and the direct (-) Kohn–Sham energy gaps , respectively, calculated with different exchange-correlation functionals. The last row gives the energy difference per functional unit cell with respect to the high-temperature simple cubic perovskite phase.