SrEuNb4O12 crystallizes in the orthorhombic Amm2 space group. Sr(1) is bonded to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(4) atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra and faces with eight equivalent Nb(1)O6 octahedra. Eu(1) is bonded in a 10-coordinate geometry to two equivalent O(3), four equivalent O(1), and four equivalent O(5) atoms. Nb(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form NbO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and faces with two equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 14-20°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Sr(1), one Eu(1), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Sr(1) and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Eu(1), and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Sr(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Eu(1) and two equivalent Nb(1) atoms.
SrEuNb4O12 crystallizes in the orthorhombic Amm2 space group. Sr(1) is bonded to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(4) atoms to form distorted SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra and faces with eight equivalent Nb(1)O6 octahedra. Both Sr(1)-O(2) bond lengths are 2.54 Å. Both Sr(1)-O(3) bond lengths are 2.84 Å. All Sr(1)-O(1) bond lengths are 3.02 Å. There are two shorter (2.59 Å) and two longer (3.07 Å) Sr(1)-O(4) bond lengths. Eu(1) is bonded in a 10-coordinate geometry to two equivalent O(3), four equivalent O(1), and four equivalent O(5) atoms. Both Eu(1)-O(3) bond lengths are 2.76 Å. All Eu(1)-O(1) bond lengths are 2.63 Å. There are two shorter (2.70 Å) and two longer (2.96 Å) Eu(1)-O(5) bond lengths. Nb(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form NbO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and faces with two equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 14-20°. The Nb(1)-O(2) bond length is 2.01 Å. The Nb(1)-O(3) bond length is 2.02 Å. The Nb(1)-O(4) bond length is 2.02 Å. The Nb(1)-O(5) bond length is 2.02 Å. There is one shorter (2.02 Å) and one longer (2.03 Å) Nb(1)-O(1) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Sr(1), one Eu(1), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Sr(1) and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(1), one Eu(1), and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Sr(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Eu(1) and two equivalent Nb(1) atoms.