CsNaEuNb5O15 crystallizes in the orthorhombic Pmc2_1 space group. Cs(1) is bonded in a 10-coordinate geometry to one O(10), one O(8), four equivalent O(2), and four equivalent O(6) atoms. Na(1) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(9) atoms. Eu(1) is bonded in a 10-coordinate geometry to one O(10), one O(8), two equivalent O(3), two equivalent O(4), and four equivalent O(7) atoms. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(4), one O(6), one O(7), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 19-35°. In the second Nb site, Nb(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 19-34°. In the third Nb site, Nb(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-32°. There are ten inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Cs(1), one Nb(1), and one Nb(3) atom. In the second O site, O(7) is bonded to two equivalent Eu(1), one Nb(1), and one Nb(2) atom to form distorted OEu2Nb2 tetrahedra that share  a cornercorner with one O(5)Na2Nb2 tetrahedra,  a cornercorner with one O(9)Na2Nb2 tetrahedra, corners with four equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(7)Eu2Nb2 tetrahedra, and edges with two equivalent O(3)NaEuNb2 trigonal pyramids. In the third O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Eu(1), and two equivalent Nb(2) atoms. In the fourth O site, O(9) is bonded to two equivalent Na(1) and two equivalent Nb(1) atoms to form distorted ONa2Nb2 tetrahedra that share corners with two equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(5)Na2Nb2 tetrahedra, corners with two equivalent O(9)Na2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(5)Na2Nb2 tetrahedra, and edges with two equivalent O(3)NaEuNb2 trigonal pyramids. In the fifth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Eu(1), and two equivalent Nb(1) atoms. In the sixth O site, O(1) is bonded in a linear geometry to two equivalent Nb(3) atoms. In the seventh O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Cs(1), one Nb(2), and one Nb(3) atom. In the eighth O site, O(3) is bonded to one Na(1), one Eu(1), one Nb(1), and one Nb(2) atom to form distorted ONaEuNb2 trigonal pyramids that share  a cornercorner with one O(5)Na2Nb2 tetrahedra,  a cornercorner with one O(9)Na2Nb2 tetrahedra, corners with two equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(5)Na2Nb2 tetrahedra,  an edgeedge with one O(9)Na2Nb2 tetrahedra, and edges with two equivalent O(7)Eu2Nb2 tetrahedra. In the ninth O site, O(4) is bonded in a 3-coordinate geometry to one Eu(1), one Nb(1), and one Nb(2) atom. In the tenth O site, O(5) is bonded to two equivalent Na(1) and two equivalent Nb(2) atoms to form distorted ONa2Nb2 tetrahedra that share corners with two equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(5)Na2Nb2 tetrahedra, corners with two equivalent O(9)Na2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(9)Na2Nb2 tetrahedra, and edges with two equivalent O(3)NaEuNb2 trigonal pyramids.
CsNaEuNb5O15 crystallizes in the orthorhombic Pmc2_1 space group. Cs(1) is bonded in a 10-coordinate geometry to one O(10), one O(8), four equivalent O(2), and four equivalent O(6) atoms. The Cs(1)-O(10) bond length is 3.41 Å. The Cs(1)-O(8) bond length is 3.44 Å. There are two shorter (3.45 Å) and two longer (3.47 Å) Cs(1)-O(2) bond lengths. All Cs(1)-O(6) bond lengths are 3.43 Å. Na(1) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(9) atoms. Both Na(1)-O(3) bond lengths are 2.46 Å. There is one shorter (2.41 Å) and one longer (2.60 Å) Na(1)-O(5) bond length. There is one shorter (2.41 Å) and one longer (2.62 Å) Na(1)-O(9) bond length. Eu(1) is bonded in a 10-coordinate geometry to one O(10), one O(8), two equivalent O(3), two equivalent O(4), and four equivalent O(7) atoms. The Eu(1)-O(10) bond length is 2.80 Å. The Eu(1)-O(8) bond length is 2.80 Å. Both Eu(1)-O(3) bond lengths are 2.62 Å. Both Eu(1)-O(4) bond lengths are 2.57 Å. There are two shorter (2.45 Å) and two longer (2.46 Å) Eu(1)-O(7) bond lengths. There are three inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(10), one O(3), one O(4), one O(6), one O(7), and one O(9) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 19-35°. The Nb(1)-O(10) bond length is 2.01 Å. The Nb(1)-O(3) bond length is 2.01 Å. The Nb(1)-O(4) bond length is 2.04 Å. The Nb(1)-O(6) bond length is 1.91 Å. The Nb(1)-O(7) bond length is 2.16 Å. The Nb(1)-O(9) bond length is 1.99 Å. In the second Nb site, Nb(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 19-34°. The Nb(2)-O(2) bond length is 1.91 Å. The Nb(2)-O(3) bond length is 2.04 Å. The Nb(2)-O(4) bond length is 2.00 Å. The Nb(2)-O(5) bond length is 1.99 Å. The Nb(2)-O(7) bond length is 2.14 Å. The Nb(2)-O(8) bond length is 2.01 Å. In the third Nb site, Nb(3) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-32°. There is one shorter (1.83 Å) and one longer (2.15 Å) Nb(3)-O(1) bond length. Both Nb(3)-O(2) bond lengths are 2.03 Å. Both Nb(3)-O(6) bond lengths are 2.04 Å. There are ten inequivalent O sites. In the first O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Cs(1), one Nb(1), and one Nb(3) atom. In the second O site, O(7) is bonded to two equivalent Eu(1), one Nb(1), and one Nb(2) atom to form distorted OEu2Nb2 tetrahedra that share  a cornercorner with one O(5)Na2Nb2 tetrahedra,  a cornercorner with one O(9)Na2Nb2 tetrahedra, corners with four equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(7)Eu2Nb2 tetrahedra, and edges with two equivalent O(3)NaEuNb2 trigonal pyramids. In the third O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Eu(1), and two equivalent Nb(2) atoms. In the fourth O site, O(9) is bonded to two equivalent Na(1) and two equivalent Nb(1) atoms to form distorted ONa2Nb2 tetrahedra that share corners with two equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(5)Na2Nb2 tetrahedra, corners with two equivalent O(9)Na2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(5)Na2Nb2 tetrahedra, and edges with two equivalent O(3)NaEuNb2 trigonal pyramids. In the fifth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Eu(1), and two equivalent Nb(1) atoms. In the sixth O site, O(1) is bonded in a linear geometry to two equivalent Nb(3) atoms. In the seventh O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Cs(1), one Nb(2), and one Nb(3) atom. In the eighth O site, O(3) is bonded to one Na(1), one Eu(1), one Nb(1), and one Nb(2) atom to form distorted ONaEuNb2 trigonal pyramids that share  a cornercorner with one O(5)Na2Nb2 tetrahedra,  a cornercorner with one O(9)Na2Nb2 tetrahedra, corners with two equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(5)Na2Nb2 tetrahedra,  an edgeedge with one O(9)Na2Nb2 tetrahedra, and edges with two equivalent O(7)Eu2Nb2 tetrahedra. In the ninth O site, O(4) is bonded in a 3-coordinate geometry to one Eu(1), one Nb(1), and one Nb(2) atom. In the tenth O site, O(5) is bonded to two equivalent Na(1) and two equivalent Nb(2) atoms to form distorted ONa2Nb2 tetrahedra that share corners with two equivalent O(7)Eu2Nb2 tetrahedra, corners with two equivalent O(5)Na2Nb2 tetrahedra, corners with two equivalent O(9)Na2Nb2 tetrahedra, corners with two equivalent O(3)NaEuNb2 trigonal pyramids,  an edgeedge with one O(9)Na2Nb2 tetrahedra, and edges with two equivalent O(3)NaEuNb2 trigonal pyramids.