BeCeSiHO5 crystallizes in the monoclinic P2_1/c space group. Be(1) is bonded to one O(2), one O(5), and two equivalent O(1) atoms to form BeO4 trigonal pyramids that share corners with three equivalent Si(1)O4 tetrahedra and  an edgeedge with one Be(1)O4 trigonal pyramid. Ce(1) is bonded in a 6-coordinate geometry to one O(2), one O(5), two equivalent O(3), and two equivalent O(4) atoms. 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 three equivalent Be(1)O4 trigonal pyramids. H(1) is bonded in a single-bond geometry to one O(5) atom. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to two equivalent Be(1) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Be(1), one Ce(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ce(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Ce(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Be(1), one Ce(1), and one H(1) atom.
BeCeSiHO5 crystallizes in the monoclinic P2_1/c space group. Be(1) is bonded to one O(2), one O(5), and two equivalent O(1) atoms to form BeO4 trigonal pyramids that share corners with three equivalent Si(1)O4 tetrahedra and  an edgeedge with one Be(1)O4 trigonal pyramid. The Be(1)-O(2) bond length is 1.60 Å. The Be(1)-O(5) bond length is 1.63 Å. Both Be(1)-O(1) bond lengths are 1.63 Å. Ce(1) is bonded in a 6-coordinate geometry to one O(2), one O(5), two equivalent O(3), and two equivalent O(4) atoms. The Ce(1)-O(2) bond length is 2.42 Å. The Ce(1)-O(5) bond length is 2.57 Å. There is one shorter (2.35 Å) and one longer (2.36 Å) Ce(1)-O(3) bond length. There is one shorter (2.34 Å) and one longer (2.54 Å) Ce(1)-O(4) bond length. 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 three equivalent Be(1)O4 trigonal pyramids. The Si(1)-O(1) bond length is 1.65 Å. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(4) bond length is 1.62 Å. H(1) is bonded in a single-bond geometry to one O(5) atom. The H(1)-O(5) bond length is 0.98 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted T-shaped geometry to two equivalent Be(1) and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Be(1), one Ce(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ce(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Ce(1) and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Be(1), one Ce(1), and one H(1) atom.