Na2BaO2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a distorted trigonal planar geometry to three equivalent O(1) atoms. In the second Na site, Na(2) is bonded to one O(1) and three equivalent O(2) atoms to form a mixture of distorted edge and corner-sharing NaO4 tetrahedra. Ba(1) is bonded in a rectangular see-saw-like geometry to one O(1) and three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), three equivalent Na(1), and one Ba(1) atom to form distorted OBaNa4 trigonal bipyramids that share corners with four equivalent O(2)Ba3Na3 octahedra, corners with four equivalent O(1)BaNa4 trigonal bipyramids,  an edgeedge with one O(2)Ba3Na3 octahedra, and  an edgeedge with one O(1)BaNa4 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 27-67°. In the second O site, O(2) is bonded to three equivalent Na(2) and three equivalent Ba(1) atoms to form distorted OBa3Na3 octahedra that share corners with four equivalent O(1)BaNa4 trigonal bipyramids, edges with six equivalent O(2)Ba3Na3 octahedra, and  an edgeedge with one O(1)BaNa4 trigonal bipyramid.
Na2BaO2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a distorted trigonal planar geometry to three equivalent O(1) atoms. There are a spread of Na(1)-O(1) bond distances ranging from 2.28-2.33 Å. In the second Na site, Na(2) is bonded to one O(1) and three equivalent O(2) atoms to form a mixture of distorted edge and corner-sharing NaO4 tetrahedra. The Na(2)-O(1) bond length is 2.31 Å. There are a spread of Na(2)-O(2) bond distances ranging from 2.35-2.64 Å. Ba(1) is bonded in a rectangular see-saw-like geometry to one O(1) and three equivalent O(2) atoms. The Ba(1)-O(1) bond length is 2.62 Å. There are a spread of Ba(1)-O(2) bond distances ranging from 2.57-2.69 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), three equivalent Na(1), and one Ba(1) atom to form distorted OBaNa4 trigonal bipyramids that share corners with four equivalent O(2)Ba3Na3 octahedra, corners with four equivalent O(1)BaNa4 trigonal bipyramids,  an edgeedge with one O(2)Ba3Na3 octahedra, and  an edgeedge with one O(1)BaNa4 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 27-67°. In the second O site, O(2) is bonded to three equivalent Na(2) and three equivalent Ba(1) atoms to form distorted OBa3Na3 octahedra that share corners with four equivalent O(1)BaNa4 trigonal bipyramids, edges with six equivalent O(2)Ba3Na3 octahedra, and  an edgeedge with one O(1)BaNa4 trigonal bipyramid.