Consistent Atomic Geometries and Electronic Structure of Five Phases of Potassium Niobate from Density-Functional Theory

Table 3

Lattice parameters and , angle , ratio , equilibrium unit-cell volume , atomic displacements in percent of , and total-energy difference per formula unit with respect to cubic calculated with different exchange-correlation functionals for the orthorhombic phase of . Data in brackets represent relative deviations from the experimental values in percent.

	LDA	PBE	PBEsol	AM05	RTPSS
(Å)	3.940 ()	3.983 ()	3.961 ()	3.958 ()	3.984 ()	3.973
(Å)	3.971 ()	4.100 ()	4.021 ()	4.043 ()	4.048 ()	4.035
(°)	89.91 ()	89.66 ()	89.82 ()	89.76 ()	89.81 ()	89.73
	0.9922 ()	0.9715 ()	0.9851 ()	0.9790 ()	0.9842 ()	0.9846
()	62.13 ()	66.95 ()	64.04 ()	64.70 ()	65.28 ()	64.68
K	0.632	1.095	0.877	0.987	0.971	0.974
Nb	0	0	0	0	0	0
O1	1.793	2.942	2.306	2.618	2.381	2.568
O2	1.615	2.768	2.131	2.432	2.216	2.413
O3	1.615	2.768	2.131	2.432	2.216	2.413
(eV)

[41]; measured at 295 K.