Li2CuSiO4 is beta beryllia-derived structured and 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(1), one O(2), one O(3), and one O(4) atom to form LiO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra, corners with four equivalent Cu(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. In the second Li site, Li(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form LiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Cu(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O4 tetrahedra. Cu(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CuO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra, corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. 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 corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, and corners with four equivalent Cu(1)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form a mixture of edge and corner-sharing OLi2CuSi tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form a mixture of edge and corner-sharing OLi2CuSi tetrahedra. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2CuSi trigonal pyramids. In the fourth O site, O(4) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form distorted corner-sharing OLi2CuSi tetrahedra.
Li2CuSiO4 is beta beryllia-derived structured and 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(1), one O(2), one O(3), and one O(4) atom to form LiO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra, corners with four equivalent Cu(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. The Li(1)-O(1) bond length is 1.97 Å. The Li(1)-O(2) bond length is 2.05 Å. The Li(1)-O(3) bond length is 2.00 Å. The Li(1)-O(4) bond length is 1.95 Å. In the second Li site, Li(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form LiO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with two equivalent Cu(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra,  an edgeedge with one Li(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O4 tetrahedra. The Li(2)-O(1) bond length is 2.00 Å. The Li(2)-O(2) bond length is 1.96 Å. The Li(2)-O(3) bond length is 2.06 Å. The Li(2)-O(4) bond length is 1.96 Å. Cu(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CuO4 tetrahedra that share corners with two equivalent Li(2)O4 tetrahedra, corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. The Cu(1)-O(1) bond length is 2.00 Å. The Cu(1)-O(2) bond length is 1.96 Å. The Cu(1)-O(3) bond length is 1.95 Å. The Cu(1)-O(4) bond length is 2.04 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 corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, and corners with four equivalent Cu(1)O4 tetrahedra. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(2) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.64 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form a mixture of edge and corner-sharing OLi2CuSi tetrahedra. In the second O site, O(2) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form a mixture of edge and corner-sharing OLi2CuSi tetrahedra. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OLi2CuSi trigonal pyramids. In the fourth O site, O(4) is bonded to one Li(1), one Li(2), one Cu(1), and one Si(1) atom to form distorted corner-sharing OLi2CuSi tetrahedra.