Li3FeCAsO7 crystallizes in the triclinic P-1 space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(6), and one O(7) atom. In the second Li site, Li(2) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Fe(1)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Li(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 59-87°. In the third Li site, Li(3) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Fe(1)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Li(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 59-88°. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted FeO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra, corners with two equivalent Li(2)O5 trigonal bipyramids, corners with two equivalent Li(3)O5 trigonal bipyramids,  an edgeedge with one Li(2)O5 trigonal bipyramid, and  an edgeedge with one Li(3)O5 trigonal bipyramid. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. As(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form AsO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with three equivalent Li(2)O5 trigonal bipyramids, and corners with three equivalent Li(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 46-66°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Li(2), one Li(3), and one C(1) atom to form a mixture of corner and edge-sharing OLi3C tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one C(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Li(2), one Li(3), one Fe(1), and one C(1) atom. In the fourth O site, O(4) is bonded to one Li(2), one Li(3), one Fe(1), and one As(1) atom to form OLi2FeAs tetrahedra that share corners with three equivalent O(6)Li2FeAs trigonal pyramids, corners with three equivalent O(7)Li2FeAs trigonal pyramids, corners with four equivalent O(5)Li2FeAs trigonal pyramids, and  an edgeedge with one O(1)Li3C tetrahedra. In the fifth O site, O(5) is bonded to one Li(2), one Li(3), one Fe(1), and one As(1) atom to form distorted OLi2FeAs trigonal pyramids that share corners with two equivalent O(1)Li3C tetrahedra, corners with four equivalent O(4)Li2FeAs tetrahedra,  a cornercorner with one O(6)Li2FeAs trigonal pyramid,  a cornercorner with one O(7)Li2FeAs trigonal pyramid,  an edgeedge with one O(6)Li2FeAs trigonal pyramid, and  an edgeedge with one O(7)Li2FeAs trigonal pyramid. In the sixth O site, O(6) is bonded to one Li(1), one Li(2), one Fe(1), and one As(1) atom to form distorted OLi2FeAs trigonal pyramids that share corners with two equivalent O(1)Li3C tetrahedra, corners with three equivalent O(4)Li2FeAs tetrahedra,  a cornercorner with one O(5)Li2FeAs trigonal pyramid,  a cornercorner with one O(7)Li2FeAs trigonal pyramid,  an edgeedge with one O(5)Li2FeAs trigonal pyramid, and  an edgeedge with one O(7)Li2FeAs trigonal pyramid. In the seventh O site, O(7) is bonded to one Li(1), one Li(3), one Fe(1), and one As(1) atom to form distorted OLi2FeAs trigonal pyramids that share corners with two equivalent O(1)Li3C tetrahedra, corners with three equivalent O(4)Li2FeAs tetrahedra,  a cornercorner with one O(5)Li2FeAs trigonal pyramid,  a cornercorner with one O(6)Li2FeAs trigonal pyramid,  an edgeedge with one O(5)Li2FeAs trigonal pyramid, and  an edgeedge with one O(6)Li2FeAs trigonal pyramid.
Li3FeCAsO7 crystallizes in the triclinic P-1 space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(6), and one O(7) atom. The Li(1)-O(1) bond length is 2.04 Å. The Li(1)-O(2) bond length is 1.92 Å. The Li(1)-O(6) bond length is 2.19 Å. The Li(1)-O(7) bond length is 2.18 Å. In the second Li site, Li(2) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Fe(1)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Li(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 59-87°. The Li(2)-O(1) bond length is 2.10 Å. The Li(2)-O(3) bond length is 2.31 Å. The Li(2)-O(4) bond length is 2.27 Å. The Li(2)-O(5) bond length is 2.17 Å. The Li(2)-O(6) bond length is 2.13 Å. In the third Li site, Li(3) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(7) atom to form distorted LiO5 trigonal bipyramids that share corners with two equivalent Fe(1)O6 octahedra, corners with three equivalent As(1)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and edges with two equivalent Li(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 59-88°. The Li(3)-O(1) bond length is 2.09 Å. The Li(3)-O(3) bond length is 2.39 Å. The Li(3)-O(4) bond length is 2.25 Å. The Li(3)-O(5) bond length is 2.15 Å. The Li(3)-O(7) bond length is 2.13 Å. Fe(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted FeO6 octahedra that share corners with four equivalent As(1)O4 tetrahedra, corners with two equivalent Li(2)O5 trigonal bipyramids, corners with two equivalent Li(3)O5 trigonal bipyramids,  an edgeedge with one Li(2)O5 trigonal bipyramid, and  an edgeedge with one Li(3)O5 trigonal bipyramid. The Fe(1)-O(2) bond length is 2.29 Å. The Fe(1)-O(3) bond length is 2.26 Å. The Fe(1)-O(4) bond length is 2.20 Å. The Fe(1)-O(5) bond length is 2.18 Å. The Fe(1)-O(6) bond length is 2.04 Å. The Fe(1)-O(7) bond length is 2.04 Å. C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. The C(1)-O(1) bond length is 1.30 Å. The C(1)-O(2) bond length is 1.29 Å. The C(1)-O(3) bond length is 1.31 Å. As(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form AsO4 tetrahedra that share corners with four equivalent Fe(1)O6 octahedra, corners with three equivalent Li(2)O5 trigonal bipyramids, and corners with three equivalent Li(3)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 46-66°. The As(1)-O(4) bond length is 1.73 Å. The As(1)-O(5) bond length is 1.71 Å. The As(1)-O(6) bond length is 1.73 Å. The As(1)-O(7) bond length is 1.73 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Li(2), one Li(3), and one C(1) atom to form a mixture of corner and edge-sharing OLi3C tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Li(1), one Fe(1), and one C(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Li(2), one Li(3), one Fe(1), and one C(1) atom. In the fourth O site, O(4) is bonded to one Li(2), one Li(3), one Fe(1), and one As(1) atom to form OLi2FeAs tetrahedra that share corners with three equivalent O(6)Li2FeAs trigonal pyramids, corners with three equivalent O(7)Li2FeAs trigonal pyramids, corners with four equivalent O(5)Li2FeAs trigonal pyramids, and  an edgeedge with one O(1)Li3C tetrahedra. In the fifth O site, O(5) is bonded to one Li(2), one Li(3), one Fe(1), and one As(1) atom to form distorted OLi2FeAs trigonal pyramids that share corners with two equivalent O(1)Li3C tetrahedra, corners with four equivalent O(4)Li2FeAs tetrahedra,  a cornercorner with one O(6)Li2FeAs trigonal pyramid,  a cornercorner with one O(7)Li2FeAs trigonal pyramid,  an edgeedge with one O(6)Li2FeAs trigonal pyramid, and  an edgeedge with one O(7)Li2FeAs trigonal pyramid. In the sixth O site, O(6) is bonded to one Li(1), one Li(2), one Fe(1), and one As(1) atom to form distorted OLi2FeAs trigonal pyramids that share corners with two equivalent O(1)Li3C tetrahedra, corners with three equivalent O(4)Li2FeAs tetrahedra,  a cornercorner with one O(5)Li2FeAs trigonal pyramid,  a cornercorner with one O(7)Li2FeAs trigonal pyramid,  an edgeedge with one O(5)Li2FeAs trigonal pyramid, and  an edgeedge with one O(7)Li2FeAs trigonal pyramid. In the seventh O site, O(7) is bonded to one Li(1), one Li(3), one Fe(1), and one As(1) atom to form distorted OLi2FeAs trigonal pyramids that share corners with two equivalent O(1)Li3C tetrahedra, corners with three equivalent O(4)Li2FeAs tetrahedra,  a cornercorner with one O(5)Li2FeAs trigonal pyramid,  a cornercorner with one O(6)Li2FeAs trigonal pyramid,  an edgeedge with one O(5)Li2FeAs trigonal pyramid, and  an edgeedge with one O(6)Li2FeAs trigonal pyramid.