Li2CuAsO4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted LiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra and corners with four equivalent As(1)O4 tetrahedra. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(4) atoms. Cu(1) is bonded in a 2-coordinate geometry to one O(2), one O(3), and two equivalent O(4) atoms. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Li(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(2), two equivalent Li(1), and one As(1) atom to form distorted OLi3As tetrahedra that share corners with two equivalent O(1)Li3As tetrahedra, corners with two equivalent O(2)Li2CuAs trigonal pyramids, and  an edgeedge with one O(2)Li2CuAs trigonal pyramid. In the second O site, O(2) is bonded to one Li(1), one Li(2), one Cu(1), and one As(1) atom to form a mixture of distorted corner and edge-sharing OLi2CuAs trigonal pyramids. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(1), one Cu(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Li(2), two equivalent Cu(1), and one As(1) atom.
Li2CuAsO4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form distorted LiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra and corners with four equivalent As(1)O4 tetrahedra. The Li(1)-O(2) bond length is 2.07 Å. The Li(1)-O(3) bond length is 2.01 Å. There is one shorter (1.99 Å) and one longer (2.02 Å) Li(1)-O(1) bond length. In the second Li site, Li(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(4) atoms. The Li(2)-O(1) bond length is 2.47 Å. The Li(2)-O(2) bond length is 2.01 Å. There is one shorter (1.97 Å) and one longer (2.30 Å) Li(2)-O(4) bond length. Cu(1) is bonded in a 2-coordinate geometry to one O(2), one O(3), and two equivalent O(4) atoms. The Cu(1)-O(2) bond length is 1.93 Å. The Cu(1)-O(3) bond length is 1.91 Å. There is one shorter (2.40 Å) and one longer (2.55 Å) Cu(1)-O(4) bond length. As(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AsO4 tetrahedra that share corners with four equivalent Li(1)O4 tetrahedra. The As(1)-O(1) bond length is 1.71 Å. The As(1)-O(2) bond length is 1.75 Å. The As(1)-O(3) bond length is 1.74 Å. The As(1)-O(4) bond length is 1.73 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(2), two equivalent Li(1), and one As(1) atom to form distorted OLi3As tetrahedra that share corners with two equivalent O(1)Li3As tetrahedra, corners with two equivalent O(2)Li2CuAs trigonal pyramids, and  an edgeedge with one O(2)Li2CuAs trigonal pyramid. In the second O site, O(2) is bonded to one Li(1), one Li(2), one Cu(1), and one As(1) atom to form a mixture of distorted corner and edge-sharing OLi2CuAs trigonal pyramids. In the third O site, O(3) is bonded in a trigonal planar geometry to one Li(1), one Cu(1), and one As(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to two equivalent Li(2), two equivalent Cu(1), and one As(1) atom.