The crystal structures of lomonosovite, ideally Na10Ti4(Si2O7)2(PO4)2 O4, a = 5.4170(7) Å, b = 7.1190(9) Å, c = 14.487(2) Å, α = 99.957(3)°, β = 96.711(3)°, γ = 90.360(3)°, V = 546.28(4) Å3, Dcalc. = 3.175 g cm-3, and murmanite, ideally Na4Ti4(Si2O7)2O4(H2O)4, a = 5.3875(6) Å, b = 7.0579(7) Å, c = 12.176(1) Å, α = 93.511(2)°, β = 107.943(4)°, γ = 90.093(2)°, V = 439.55(2) Å3, Dcalc. = 2.956 g.cm-3, from the Lovozero alkaline massif, Kola Peninsula, Russia, have been refined in the space group P

\({\bar{1}}\)
(Z = 1) to R values of 2.64 and 4.47%, respectively, using 4572 and 2222 observed |Fo ≥ 4σF| reflections collected with a single-crystal Bruker AXS SMART APEX diffractometer with a CCD detector and Mo-Kα radiation. Electron microprobe analysis gave empirical formulae for lomonosovite
\((\mathrm{Na}_{9.50}\mathrm{Mn}_{0.16}\mathrm{Ca}_{0.11})_{{{\sum}}9.77}(\mathrm{Ti}_{2.83}^{4+}\mathrm{Nb}_{0.51}\mathrm{Mn}_{0.27}^{2+}\mathrm{Zr}_{0.11}\mathrm{Mg}_{0.11}\mathrm{Fe}_{0.10}^{2+}\mathrm{Fe}_{0.06}^{3+}\mathrm{Ta}_{0.01})_{{{\sum}}4.00}(\mathrm{Si}_{2.02}\mathrm{O}_{7})_{2}(\mathrm{P}_{0.98}\mathrm{O}_{4})_{2}(\mathrm{O}_{3.50}\mathrm{F}_{0.50})_{{{\sum}}4},{\ }Z{\ }={\ }1\)
⁠, calculated on the basis of 26(O+F) a.p.f.u., and murmanite
\((\mathrm{Na}_{3.32}\mathrm{Mn}_{0.15}\mathrm{Ca}_{0.21}\mathrm{K}_{0.05})_{{{\sum}}3.73}(\mathrm{Ti}_{3.08}^{4+}\mathrm{Nb}_{0.51}\mathrm{Mn}_{0.18}^{2+}\mathrm{Fe}_{0.15}^{3+}\mathrm{Mg}_{0.07}\mathrm{Zr}_{0.01})_{{{\sum}}4.00}(\mathrm{Si}_{1.98}\mathrm{O}_{7})_{2}(\mathrm{O}_{3.76}\mathrm{F}_{0.24})_{{{\sum}}4}(\mathrm{H}_{2}\mathrm{O})_{4}\)
⁠, Z = 1, calculated on the basis of 22(O+F) a.p.f.u., with H2O determined from structure refinement and Fe3+/(Fe2++Fe3+) ratios obtained by Mössbauer spectroscopy. The crystal structures of lomonosovite and murmanite are a combination of a titanium silicate (TS) block and an intermediate (I) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral), and is characterized by a planar cell based on translation vectors, t1 and t2, with t1 ∼5.5 and t2 ∼7 Å and t1 ^ t2 close to 90°. The TS block exhibits linkage and stereochemistry typical for Group IV (Ti = 4 a.p.f.u.) of the Ti disilicate minerals: two H sheets connect to the O sheet such that two (Si2O7) groups link to Ti polyhedra of the O sheet adjacent along t1. In murmanite and lomonosovite, the invariant part of the TS block is of composition Na4Ti4(Si2O7)2O4. There is no evidence of vacancy-dominant cation sites or (OH) groups in the O sheet of lomonosovite or murmanite. In lomonosovite, the I block is a framework of Na polyhedra and P tetrahedra which gives 2[Na3 (PO)4] p.f.u. In murmanite, there are four (H2O) groups in the intermediate space between TS blocks. In lomonosovite, TS and I blocks alternate along c. In murmanite, TS blocks are connected via hydrogen bonding. The H atoms were located and details of the hydrogen bonding are discussed.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.