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

Table 2

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

P4mm	LDA	PBE	PBEsol	AM05	RTPSS
(Å)	3.989 ()	4.193 ()	4.058 ()	4.098 ()	4.085 ()	4.063
(Å)	3.945 ()	3.994 ()	3.969 ()	3.968 ()	3.992 ()	3.997
	1.0112 ()	1.0498 ()	1.0224 ()	1.0328 ()	1.0233 ()	1.0165
()	62.08 ()	66.87 ()	63.93 ()	64.52 ()	65.10 ()	64.91
K	1.072	1.762	1.462	1.635	1.634	1.8
Nb	0	0	0	0	0	0
O1	2.859	6.142	4.109	4.972	4.277	4.4
O2	3.026	4.962	3.850	4.352	3.934	4.0
O3	3.026	4.962	3.850	4.352	3.934	4.0
(eV)

[41]; measured at 543 K.