Na2MgNd2Ti2O8 crystallizes in the tetragonal P-4m2 space group. Na(1) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), and two equivalent O(4) atoms. Mg(1) is bonded in a 4-coordinate geometry to four equivalent O(2) atoms. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 9-coordinate geometry to two equivalent O(3), two equivalent O(4), and five equivalent O(1) atoms. In the second Nd site, Nd(1) is bonded in a 9-coordinate geometry to two equivalent O(3), two equivalent O(4), and five equivalent O(1) atoms. Ti(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-17°. There are four inequivalent O sites. In the first O site, O(1) is bonded to five Nd(1,1) and one Ti(1) atom to form distorted ONd5Ti octahedra that share corners with four equivalent O(1)Nd5Ti octahedra, corners with six equivalent O(3)Na2Nd2Ti2 octahedra, corners with six equivalent O(4)Na2Nd2Ti2 octahedra, edges with eight equivalent O(1)Nd5Ti octahedra, faces with two equivalent O(3)Na2Nd2Ti2 octahedra, and faces with two equivalent O(4)Na2Nd2Ti2 octahedra. The corner-sharing octahedral tilt angles range from 17-52°. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Mg(1), and one Ti(1) atom. In the third O site, O(3) is bonded to two equivalent Na(1), two equivalent Nd(1), and two equivalent Ti(1) atoms to form distorted ONa2Nd2Ti2 octahedra that share corners with two equivalent O(3)Na2Nd2Ti2 octahedra, corners with six equivalent O(1)Nd5Ti octahedra, edges with two equivalent O(3)Na2Nd2Ti2 octahedra, faces with two equivalent O(1)Nd5Ti octahedra, and faces with four equivalent O(4)Na2Nd2Ti2 octahedra. The corner-sharing octahedral tilt angles range from 17-52°. In the fourth O site, O(4) is bonded to two equivalent Na(1), two equivalent Nd(1), and two equivalent Ti(1) atoms to form distorted ONa2Nd2Ti2 octahedra that share corners with two equivalent O(4)Na2Nd2Ti2 octahedra, corners with six equivalent O(1)Nd5Ti octahedra, edges with two equivalent O(4)Na2Nd2Ti2 octahedra, faces with two equivalent O(1)Nd5Ti octahedra, and faces with four equivalent O(3)Na2Nd2Ti2 octahedra. The corner-sharing octahedral tilt angles range from 5-52°.
Na2MgNd2Ti2O8 crystallizes in the tetragonal P-4m2 space group. Na(1) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), and two equivalent O(4) atoms. The Na(1)-O(2) bond length is 2.48 Å. Both Na(1)-O(3) bond lengths are 2.49 Å. Both Na(1)-O(4) bond lengths are 2.37 Å. Mg(1) is bonded in a 4-coordinate geometry to four equivalent O(2) atoms. All Mg(1)-O(2) bond lengths are 2.13 Å. There are two inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 9-coordinate geometry to two equivalent O(3), two equivalent O(4), and five equivalent O(1) atoms. Both Nd(1)-O(3) bond lengths are 2.50 Å. Both Nd(1)-O(4) bond lengths are 2.63 Å. There is one shorter (2.29 Å) and four longer (2.80 Å) Nd(1)-O(1) bond lengths. In the second Nd site, Nd(1) is bonded in a 9-coordinate geometry to two equivalent O(3), two equivalent O(4), and five equivalent O(1) atoms. Both Nd(1)-O(3) bond lengths are 2.50 Å. Both Nd(1)-O(4) bond lengths are 2.63 Å. There is one shorter (2.29 Å) and four longer (2.80 Å) Nd(1)-O(1) bond lengths. Ti(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-17°. The Ti(1)-O(1) bond length is 2.25 Å. The Ti(1)-O(2) bond length is 2.07 Å. Both Ti(1)-O(3) bond lengths are 1.98 Å. Both Ti(1)-O(4) bond lengths are 1.96 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to five Nd(1,1) and one Ti(1) atom to form distorted ONd5Ti octahedra that share corners with four equivalent O(1)Nd5Ti octahedra, corners with six equivalent O(3)Na2Nd2Ti2 octahedra, corners with six equivalent O(4)Na2Nd2Ti2 octahedra, edges with eight equivalent O(1)Nd5Ti octahedra, faces with two equivalent O(3)Na2Nd2Ti2 octahedra, and faces with two equivalent O(4)Na2Nd2Ti2 octahedra. The corner-sharing octahedral tilt angles range from 17-52°. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Mg(1), and one Ti(1) atom. In the third O site, O(3) is bonded to two equivalent Na(1), two equivalent Nd(1), and two equivalent Ti(1) atoms to form distorted ONa2Nd2Ti2 octahedra that share corners with two equivalent O(3)Na2Nd2Ti2 octahedra, corners with six equivalent O(1)Nd5Ti octahedra, edges with two equivalent O(3)Na2Nd2Ti2 octahedra, faces with two equivalent O(1)Nd5Ti octahedra, and faces with four equivalent O(4)Na2Nd2Ti2 octahedra. The corner-sharing octahedral tilt angles range from 17-52°. In the fourth O site, O(4) is bonded to two equivalent Na(1), two equivalent Nd(1), and two equivalent Ti(1) atoms to form distorted ONa2Nd2Ti2 octahedra that share corners with two equivalent O(4)Na2Nd2Ti2 octahedra, corners with six equivalent O(1)Nd5Ti octahedra, edges with two equivalent O(4)Na2Nd2Ti2 octahedra, faces with two equivalent O(1)Nd5Ti octahedra, and faces with four equivalent O(3)Na2Nd2Ti2 octahedra. The corner-sharing octahedral tilt angles range from 5-52°.