NaCu4(AsO4)3 crystallizes in the monoclinic C2/c space group. Na(1) is bonded to two equivalent O(5), two equivalent O(6), and four equivalent O(1) atoms to form distorted NaO8 hexagonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra, edges with two equivalent Na(1)O8 hexagonal bipyramids, edges with four equivalent Cu(2)O6 octahedra,  an edgeedge with one As(2)O4 tetrahedra, and edges with two equivalent As(1)O4 tetrahedra. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted square co-planar geometry to two equivalent O(2) and two equivalent O(3) atoms. In the second Cu site, Cu(2) is bonded to one O(1), one O(2), one O(5), one O(6), and two equivalent O(4) atoms to form distorted CuO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(1)O8 hexagonal bipyramids, and  an edgeedge with one Cu(2)O6 octahedra. In the third Cu site, Cu(3) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form AsO4 tetrahedra that share  a cornercorner with one Na(1)O8 hexagonal bipyramid, corners with four equivalent Cu(2)O6 octahedra, and  an edgeedge with one Na(1)O8 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 44-58°. In the second As site, As(2) is bonded to two equivalent O(2) and two equivalent O(6) atoms to form AsO4 tetrahedra that share corners with four equivalent Cu(2)O6 octahedra and  an edgeedge with one Na(1)O8 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 58-61°. There are six inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), one Cu(2), and one As(1) atom to form distorted ONa2CuAs trigonal pyramids that share corners with two equivalent O(5)NaCu2As trigonal pyramids, corners with four equivalent O(1)Na2CuAs trigonal pyramids,  an edgeedge with one O(1)Na2CuAs trigonal pyramid, and edges with two equivalent O(5)NaCu2As trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cu(1), one Cu(2), and one As(2) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Cu(1), one Cu(3), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Cu(2) and one As(1) atom. In the fifth O site, O(5) is bonded to one Na(1), one Cu(2), one Cu(3), and one As(1) atom to form distorted ONaCu2As trigonal pyramids that share corners with two equivalent O(1)Na2CuAs trigonal pyramids,  an edgeedge with one O(5)NaCu2As trigonal pyramid, and edges with two equivalent O(1)Na2CuAs trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Na(1), one Cu(2), one Cu(3), and one As(2) atom.
NaCu4(AsO4)3 crystallizes in the monoclinic C2/c space group. Na(1) is bonded to two equivalent O(5), two equivalent O(6), and four equivalent O(1) atoms to form distorted NaO8 hexagonal bipyramids that share corners with two equivalent As(1)O4 tetrahedra, edges with two equivalent Na(1)O8 hexagonal bipyramids, edges with four equivalent Cu(2)O6 octahedra,  an edgeedge with one As(2)O4 tetrahedra, and edges with two equivalent As(1)O4 tetrahedra. Both Na(1)-O(5) bond lengths are 2.65 Å. Both Na(1)-O(6) bond lengths are 2.80 Å. There are two shorter (2.51 Å) and two longer (2.65 Å) Na(1)-O(1) bond lengths. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a distorted square co-planar geometry to two equivalent O(2) and two equivalent O(3) atoms. Both Cu(1)-O(2) bond lengths are 1.91 Å. Both Cu(1)-O(3) bond lengths are 1.93 Å. In the second Cu site, Cu(2) is bonded to one O(1), one O(2), one O(5), one O(6), and two equivalent O(4) atoms to form distorted CuO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra, corners with four equivalent As(1)O4 tetrahedra, edges with two equivalent Na(1)O8 hexagonal bipyramids, and  an edgeedge with one Cu(2)O6 octahedra. The Cu(2)-O(1) bond length is 2.00 Å. The Cu(2)-O(2) bond length is 1.94 Å. The Cu(2)-O(5) bond length is 2.36 Å. The Cu(2)-O(6) bond length is 1.99 Å. There is one shorter (1.97 Å) and one longer (2.57 Å) Cu(2)-O(4) bond length. In the third Cu site, Cu(3) is bonded in a 6-coordinate geometry to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. Both Cu(3)-O(3) bond lengths are 2.00 Å. Both Cu(3)-O(5) bond lengths are 1.97 Å. Both Cu(3)-O(6) bond lengths are 2.60 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form AsO4 tetrahedra that share  a cornercorner with one Na(1)O8 hexagonal bipyramid, corners with four equivalent Cu(2)O6 octahedra, and  an edgeedge with one Na(1)O8 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 44-58°. The As(1)-O(1) bond length is 1.72 Å. The As(1)-O(3) bond length is 1.76 Å. The As(1)-O(4) bond length is 1.73 Å. The As(1)-O(5) bond length is 1.73 Å. In the second As site, As(2) is bonded to two equivalent O(2) and two equivalent O(6) atoms to form AsO4 tetrahedra that share corners with four equivalent Cu(2)O6 octahedra and  an edgeedge with one Na(1)O8 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 58-61°. Both As(2)-O(2) bond lengths are 1.79 Å. Both As(2)-O(6) bond lengths are 1.71 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), one Cu(2), and one As(1) atom to form distorted ONa2CuAs trigonal pyramids that share corners with two equivalent O(5)NaCu2As trigonal pyramids, corners with four equivalent O(1)Na2CuAs trigonal pyramids,  an edgeedge with one O(1)Na2CuAs trigonal pyramid, and edges with two equivalent O(5)NaCu2As trigonal pyramids. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Cu(1), one Cu(2), and one As(2) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Cu(1), one Cu(3), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to two equivalent Cu(2) and one As(1) atom. In the fifth O site, O(5) is bonded to one Na(1), one Cu(2), one Cu(3), and one As(1) atom to form distorted ONaCu2As trigonal pyramids that share corners with two equivalent O(1)Na2CuAs trigonal pyramids,  an edgeedge with one O(5)NaCu2As trigonal pyramid, and edges with two equivalent O(1)Na2CuAs trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Na(1), one Cu(2), one Cu(3), and one As(2) atom.