Li2CuPO4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form distorted LiO4 tetrahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Cu(1)O4 tetrahedra, and  an edgeedge with one P(1)O4 tetrahedra. In the second Li site, Li(2) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form LiO4 tetrahedra that share corners with two equivalent Cu(1)O4 tetrahedra, corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. Cu(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms 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 P(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O4 tetrahedra. P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Cu(1)O4 tetrahedra, and  an edgeedge with one Li(1)O4 tetrahedra. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Li(1), two equivalent Cu(1), and one P(1) atom. In the second O site, O(2) is bonded to one Li(1), two equivalent Li(2), and one P(1) atom to form OLi3P tetrahedra that share corners with eight equivalent O(3)Li2CuP trigonal pyramids and  an edgeedge with one O(2)Li3P tetrahedra. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Cu(1), and one P(1) atom to form distorted OLi2CuP trigonal pyramids that share corners with four equivalent O(2)Li3P tetrahedra, corners with two equivalent O(3)Li2CuP trigonal pyramids, and  an edgeedge with one O(3)Li2CuP trigonal pyramid.
Li2CuPO4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Li sites. In the first Li site, Li(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form distorted LiO4 tetrahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Cu(1)O4 tetrahedra, and  an edgeedge with one P(1)O4 tetrahedra. The Li(1)-O(1) bond length is 1.99 Å. The Li(1)-O(2) bond length is 2.02 Å. Both Li(1)-O(3) bond lengths are 2.09 Å. In the second Li site, Li(2) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form LiO4 tetrahedra that share corners with two equivalent Cu(1)O4 tetrahedra, corners with four equivalent Li(1)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra, and  an edgeedge with one Li(2)O4 tetrahedra. Both Li(2)-O(2) bond lengths are 2.01 Å. Both Li(2)-O(3) bond lengths are 1.94 Å. Cu(1) is bonded to two equivalent O(1) and two equivalent O(3) atoms 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 P(1)O4 tetrahedra, and  an edgeedge with one Cu(1)O4 tetrahedra. Both Cu(1)-O(1) bond lengths are 2.15 Å. Both Cu(1)-O(3) bond lengths are 2.05 Å. P(1) is bonded to one O(1), one O(2), and two equivalent O(3) atoms to form PO4 tetrahedra that share corners with two equivalent Li(1)O4 tetrahedra, corners with four equivalent Li(2)O4 tetrahedra, corners with four equivalent Cu(1)O4 tetrahedra, and  an edgeedge with one Li(1)O4 tetrahedra. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(2) bond length is 1.55 Å. Both P(1)-O(3) bond lengths are 1.56 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Li(1), two equivalent Cu(1), and one P(1) atom. In the second O site, O(2) is bonded to one Li(1), two equivalent Li(2), and one P(1) atom to form OLi3P tetrahedra that share corners with eight equivalent O(3)Li2CuP trigonal pyramids and  an edgeedge with one O(2)Li3P tetrahedra. In the third O site, O(3) is bonded to one Li(1), one Li(2), one Cu(1), and one P(1) atom to form distorted OLi2CuP trigonal pyramids that share corners with four equivalent O(2)Li3P tetrahedra, corners with two equivalent O(3)Li2CuP trigonal pyramids, and  an edgeedge with one O(3)Li2CuP trigonal pyramid.