Supplementary material

Table S1. Atomic parameters and bond parameters for BaNbO2N and SrM0.2Nb0.8O3xNx (M = Li, Na, Mg) determined from neutron Rietveld

refinement.

BaNbO2N BaLi0.2Nb0.8O2.8N0.2 BaNa0.2Nb0.8O2.8N0.2 BaMg0.2Nb0.8O2.6N0.4

Ba (1a; 0, 0, 0) occ

Uiso (Å2)

Ba1

0.0027(4)

Ba1

0.0071(4)

Ba1

0.0070(5)

Ba1

0.0070(4)

M/Nb (1b; ½, ½, ½) occ

Uiso (Å2)

Nb1

0.0091(3)

Li0.188(4)Nb0.812

0.0074(4)

Na0.21(1)Nb0.79

0.0065(4)

Mg0.192(4)Nb0.808

0.0108(3)

X (1c; ½, 0, ½) occ

Uiso (Å2)

O0.70(1)N0.30

0.0079(2)

O0.93(1)N0.07

0.0110(2)

O0.92(1)N0.08

0.0171(3)

O0.84(1)N0.16

0.0076(2)

NbX (Å) [6 ] 2.06192(2) 2.05774(2) 2.07288(3) 2.05986(2)

NbXNb () [3 ] 180 180 180 180

a: SrLi0.2Nb0.8O2.8N0.2

b: SrNa0.2Nb0.8O2.8N0.2

c: SrMg0.2Nb0.8O2.6N0.4

d: SrNbO2N

e: BaLi0.2Nb0.8O2.8N0.2 f: BaNa0.2Nb0.8O2.8N0.2g: BaMg0.2Nb0.8O2.6N0.4

h: BaNbO2N

i: SrLi0.2Ta0.8O2.8N0.2

j: SrNa0.2Ta0.8O2.8N0.2

k: SrMg0.2Ta0.8O2.6N0.4

l: SrTaO2N

m:BaLi0.2Ta0.8O2.8N0.2

n:BaNa0.2Ta0.8O2.8N0.2

o:BaLi0.2Ta0.8O2.8N0.2

p:BaTaO2N

Fig. S1. Photographs of simple and complex perovskite oxynitrides.