K3 Nb8 O21 Benabbas A, Borel M, Grandin A, Leclaire A, Raveau B Acta Crystallographica C49 (1993) 439-441 Single-crystal structure of K3 Nb8 O21 _cod_database_code 1001860 _database_code_amcsd 0010282 9.1584 9.1584 12.0404 90 90 120 P6_3/mcm atom x y z Nb1 2/3 1/3 0 Nb2 .24888 .24888 .09468 K1 .5938 .5938 .25 O1 .4818 .3143 .0958 O2 .2006 0 .0740 O3 .2070 .2070 .25