Sr3NbGa3Si2O14 crystallizes in the monoclinic C2 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and two equivalent O(1) atoms. In the second Sr site, Sr(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(7) atoms. Nb(1) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form NbO6 octahedra that share corners with two equivalent Ga(2)O4 tetrahedra and corners with four equivalent Ga(1)O4 tetrahedra. There are two inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form GaO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. In the second Ga site, Ga(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form GaO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Ga(2)O4 tetrahedra and corners with two equivalent Ga(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Sr(2), two equivalent Sr(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Sr(2), one Ga(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Sr(1), one Ga(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Sr(1), one Ga(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Sr(1), one Nb(1), and one Ga(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Sr(1), one Nb(1), and one Ga(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Sr(2), one Nb(1), and one Ga(1) atom.
Sr3NbGa3Si2O14 crystallizes in the monoclinic C2 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), one O(5), one O(6), and two equivalent O(1) atoms. The Sr(1)-O(3) bond length is 2.73 Å. The Sr(1)-O(4) bond length is 2.76 Å. The Sr(1)-O(5) bond length is 2.56 Å. The Sr(1)-O(6) bond length is 2.57 Å. There is one shorter (2.58 Å) and one longer (2.62 Å) Sr(1)-O(1) bond length. In the second Sr site, Sr(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(7) atoms. Both Sr(2)-O(1) bond lengths are 2.64 Å. Both Sr(2)-O(2) bond lengths are 2.72 Å. Both Sr(2)-O(7) bond lengths are 2.55 Å. Nb(1) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(7) atoms to form NbO6 octahedra that share corners with two equivalent Ga(2)O4 tetrahedra and corners with four equivalent Ga(1)O4 tetrahedra. Both Nb(1)-O(5) bond lengths are 2.03 Å. Both Nb(1)-O(6) bond lengths are 2.03 Å. Both Nb(1)-O(7) bond lengths are 2.03 Å. There are two inequivalent Ga sites. In the first Ga site, Ga(1) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form GaO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. The Ga(1)-O(3) bond length is 1.86 Å. The Ga(1)-O(4) bond length is 1.86 Å. The Ga(1)-O(6) bond length is 1.86 Å. The Ga(1)-O(7) bond length is 1.86 Å. In the second Ga site, Ga(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form GaO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 58°. Both Ga(2)-O(2) bond lengths are 1.86 Å. Both Ga(2)-O(5) bond lengths are 1.86 Å. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share  a cornercorner with one Ga(2)O4 tetrahedra and corners with two equivalent Ga(1)O4 tetrahedra. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(2) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.63 Å. The Si(1)-O(4) bond length is 1.62 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Sr(2), two equivalent Sr(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Sr(2), one Ga(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Sr(1), one Ga(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Sr(1), one Ga(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Sr(1), one Nb(1), and one Ga(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Sr(1), one Nb(1), and one Ga(1) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Sr(2), one Nb(1), and one Ga(1) atom.