Hydrogen bonding in lead uranyl oxide mineral sayrite

The hydrogen bonding in the structure of the lead uranyl-oxide mineral sayrite has been refined and described directly from XRD data for the first time. Sayrite is monoclinic, a = 10.6925(4), b = 6.9593(2), c = 13.6035(5) Å, β = 107.680(3), with V = 964.46(6) Å${}^3$, and Z = 2, space group P 2${}_1$/n. The structure has been refined to an R = 2.34% based on 2252 unique [I > 3σI] reflections. Sayrite possesses a layered structure with the uranyl-hydroxo-oxide sheets of the topology characterized by the topology symbol P${}_4$(UD)${}_8$R${}_5$. Between adjacent sheets, there are Pb${}^{2+}$ cations and molecular H${}_2$O. All H${}_2$O groups in sayrite belong to non-transformer groups, which distribute bond-valence from equally from all the cationic parts of the structure to anions. The structural formula of sayrite is Pb${}_2$(H${}_2$${}^{\left[4\right]}$O)${}_4$[(UO${}_2$)${}_5$O${}_6$(OH)${}_2$].