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

Table 2

Structural properties of the monoclinic phase of NaNbO₃.

	PBE	PBEsol	AM05	Experiment
a (Å)	5.576	5.495	5.513	5.50453 [5]
b (Å)	15.731	15.504	15.554	15.52975 [5]
c (Å)	5.640	5.559	5.576	5.56779 [5]
(Å^3)	494.719	473.596	478.138	475.95682 [5]
(GPa)	99.8	117.1	109.4	—
(GPa)	3.3	6.5	6.4	—
(eV)	2.330	2.290	2.291	—
(meV)	−111	−109	−94	—

Given are the lattice parameters a, b, 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.