Mineralogical Magazine, April 2001, Vol. 65(2), pp.297–304
Thecrystalstructure of Na 4(UO2)(CO3)3 anditsr elationshiptoschrÎckingerite
YAPING LI, S. V. KRIVOVICHEVAND P. C. BURNS* Department of Civil Engineering and Geological Sciences, University of Notre Dame, 156 Fitzpatrick, Notre Dame, Indiana 46556-0767, USA
ABSTR ACT
Crystalsof the compound Na 4(UO2)(CO3)3 havebeen synthesized and the structure has been solved. It istrigonal with a =9.3417(6), c =12.824(1)A Ê , V = 969.2(1) AÊ 3,spacegroup P3¯c1 and Z = 4. The structurewas refined on the basis of F2 (wR2 = 4.2%)forall unique data collected using Mo- Ka X- radiationand a CCD-baseddetector. The final R1 was 2.0%,calculatedfor 534 unique observed ( Fo 5 4sF)reflections,and the goodness- of-fit( S)was0.91. The structure contains a uranyltricarbonate clustercomposed of a uranylhexagonal bipyramid that shares three equatorial edges with CO 3 triangles.The uranyl tricarbonate clusters are connected through NaO 6 and NaO5 polyhedra,forming a heteropolyhedralframework structure. This compound may be related to a uranylcarbonate phase with thesame composition which has been reported as an alteration phase on the surface of Chernobyl ‘lava’,andas a mineralin the Jachymov ore district, Czech Republic.
KEY WORDS: uranylcarbonate, sodium uranyl carbonate, crystal structure, nuclear waste.
Introduction [Cu2(UO2)3(CO3)2O2(OH)2](H2O)4 (Ginderow andCesbron, 1985), rutherfordine, [(UO 2)(CO3)] MORE than25 uranyl carbonate minerals are (Finch et al. ,1999),andbijvoetite, known(Mandarino, 1999), and actinide-carbonate [M8(UO2)16O8(OH)8(H2O)25](H2O)14, M = REE, complexesare important over a widevariety of Y (Li et al.,2000).Of these, roubaul tite, environmentalconditions (Clark et al., 1995). The rutherfordineand bijvoetite each contain sheets crystalstructur esof eight uranyl carbonat e ofpolyhedra, whereas the others contain the mineralshave been reported. On the basis of the uranyltricarbonate cluster. polymerizationof cation polyhedra of higher Thereare several reports of the compound bondvalence, uranyl carbonat eshave been Na4(UO2)(CO3)3 inthe literature, although the groupedinto those containing in nite sheets and structurehas not been published. Douglass (1956) thosewith an isolated uranyl tricarbonate cluster synthesizedNa 4(UO2)(CO3)3 andprovided X -ray (Burns,1999) .Thestructures have been solved powderdiffraction (XRD) data.An unnamed forliebigite, Ca 2[(UO2)(CO3)3](H2O)11 (Mereiter, mineralwith composition Na 4(UO2)(CO3)3 was 1982),schro¨ckingerite,NaCa 3[(UO2)(CO3)3] reportedfrom the Jachymov ore district, where it (SO4)F(H2O)10 (Mereiter,1986 a),swartzite, occursas part of the secondary uranyl mineral CaMg[(UO2)(CO3)3](H2O)12 (Mereiter,1986 b), assemblage(Ondrus et al.,1997).Acompoundof andersonite,Na 2Ca[(UO 2 )(CO 3 )3 ](H 2O)5 ] thesame composition was also reported as an (Mereiter,1986 c),bayleyite,Mg 2[(UO2)(CO3)3] alterationphase on Chernobyl ‘lava’ (Burakov et (H2O)18 (Mayerand Mereiter, 1986), roubaultite, al.,1999).Recently,a mineralwith the composi- tion Na4(UO2)(CO3)3 wasapprove dbythe Commissionon New Mineralsand New Mineral Nameso ftheInt ernationalMineralogical Association(Grice and Ferraris, 2000), but *E-mail: [email protected] detailedinformation is still unavailable. Table 1
# 2001The Mineralogical Society TABLE 1. Crystallographic information reported for Na4(UO2)(CO3)3.
Sources Unit cell a (AÊ ) b (AÊ ) c (AÊ ) a (8) b (8) g (8) Refs Y
Douglass trigonal 9.32(1) 12.80(1) [1] APING Unnamed mineral from Czech triclinic 16.468(2) 27.578(3) 5.222(2) 94.155(2) 100.58(1) 121.25(1) [2]
298 hexagonal 18.621(3) 12.801(4) [2] Unnamed mineral triclinic 9.280 9.295 12.864 90.293 91.124 119.548 [3] LI Current work trigonal 9.3417(6) 12.824(1) ETAL.
[1] Douglass (1956), [2] Ondrus et al. (1997), [3] Grice and Ferraris (2000) CRYSTAL STRUCTURE OFN A4(UO2)(CO3)3
presentsa summaryof crystallographic informa- measured,of which 804 re ections were unique, tionreported for compounds with the composition with534 classed as observed ( Fo 5 4sF). Na4(UO2)(CO3)3.Wehave grown a singlecrystal of Na4(UO2)(CO3)3 usinghydrothermal techni- ques,and report the structure here. Structuresolution and ref inement TheBruker SHELXTL Version5 systemof programswas used for the determination and Experimental renement of the crystal structure. The structure Crystalsy nthesis wassolved by direct methods in spacegroup P3¯c1 2 Crystalsof Na 4(UO2)(CO3)3 weresynthesized by andwas re ned on the basis of F forall unique hydrothermalreaction of 4mlof a0.2 M solution data.The nalmodel included all atomic- ofuranylacetate with 0. 17g ofsodiumcarbonate. positionalparameters, anisotropic-disp lacement Thesolution was heated to 220 8C in a Te on- parametersfor a llatoms, and a renable linedParr bomb for 2 weeks.Yellowish anhedral weightingscheme of the structure factors. The crystalswere recovered by ltration,washed with renement converged to a wR2 of 4.2% for all de-ionizedwater, and dried in air. data, an R1 of 2.0%,calculatedfor the 534 unique observed (Fo5 4sF)reections, and a goodness- of- t (S)of0.91 for all data. The nalatomic Single-crystalXRD coordinatesand anisotropic-displac ementpara- Asinglecrystal of Na 4(UO2)(CO3)3 with dimen- metersare given in Table 3, with selected sions 0.1060.1060.10mm wasselected and interatomicdistances given in Table 4, and a mountedon a glass bre,and diffraction data bond-valenceanalysis given in Table 5. Observed werecollected using a Bruker1K SMART CCD andcalcul atedstructu refactors have been diffractometerby usingMo- Ka X-radiationand a depositedwiththePrincipalEditorof crystal-to-detectordistance of 5. 0cm.More than MineralogicalMagazine andare available upon ahemisphereof 3-dimensionaldata was collected request. usingframe widths of 0.3 8 in o,with10 s spent countingper frame. The unit- cellparameters (Table2) were re ned from 2210 re ections Discussion usingleast-squares techniques. The data were Cationcoo rdination integratedand corrected for Lorentz, polarization Thestructure of Na 4(UO2)(CO3)3 contains a andbackground effects using the Bruker program singlesymmetrically unique U 6+ cation,which 2+ SAINT. Asemi-empiricalabsorption correction ispartof anapproximately linear (UO 2) uranyl wasapplied on thebasis of equivalentre ections ion(designated Ur)withan averageU OUr bond bymodelling the crystal as an ellipsoid; the lengthof 1.81 A Ê (Table1) .Theuranyl ion is correctionreduced Rint of1646intense re ections furthercoordinated by six O atomsthat are from4. 9to4.1 %.Atotalof 5555re ections were arrangedat the equato rial(desig natedeq )
TABLE 2.Crystallographic information for Na 4(UO2)(CO3)3. a (AÊ ) 9.3417(6) Crystal size (mm) 0.1060.1060.10 c (AÊ ) 12.824(1) Total ref. 5555 V (AÊ 3) 969.2(1) Unique ref. 804 ¯ Space group P3c1 Rint (%) 5.35 F(000) 968 Unique FO54sF 534 m (mm 1) 16.986 Final wR2 (%) 4.2 3 Dcalc (g/cm ) 3.715 Final R1 (%) 2.0 S 0.91 Unit-cell contents: 4[Na 4(UO2)(CO3)3]
R1 = S(|Fo| |Fc|)/ S |Fo| 2 1/2 S = [Sw(|Fo Fc) /(m n)] , for m =804 observations and n =60 parameters 2 2 2 2 2 w = 1/[s (FO ) + (0.02176P) ], P = (max(FO ,0) + 26FC )/3
299 YAPING LI ETAL.
4 2 3 TABLE 3.Atomic coordinates ( 610 )anddisplacement parameters (A Ê 610 ) for Na4(UO2)(CO3)3.
x y z U*(eq) U11 U22 U33 U23 U13 U12
U1 6667 3333 1303(1) 11(1) 10(1) 10(1) 13(1) 0 0 5(1) Na1 0 0 2500 23(1) 22(1) 22(1) 24(2) 0 0 11(1) Na2 0 0 0 22(1) 23(1) 23(1) 20(2) 0 0 11(1) Na3 8769(3) 3076(3) 3764(2) 27(1) 13(1) 16(1) 49(1) 5(1) 1(1) 6(1) O1 6667 3333 2718(4) 20(1) 22(2) 22(2) 17(3) 0 0 11(1) O2 6667 3333 –106(4) 23(1) 30(2) 30(2) 9(3) 0 0 15(1) O3 9651(4) 7833(4) 3784(3) 21(1) 15(2) 19(2) 33(2) –3(2) –2(2) 12(2) O4 460(4) 5959(5) 3817(3) 23(1) 10(2) 10(2) 49(3) 6(2) 6(2) 5(2) O5 1471(4) 3765(5) 3563(3) 26(1) 12(2) 15(2) 55(3) –2(2) 0(2) 10(2) C1 733(7) 7444(7) 3723(4) 17(1) 11(3) 13(3) 22(3) –1(2) –4(2) 2(2)
* U(eq) is dened as one third of the trace of the orthogonalized Uij tensor
positionsof a hexagonalbipyramid. The average average Na2 Obondlength of 2.444(3) A Ê . The 6+ U Oeq bondlength is 2. 41A Ê (Table4), which Na3cation is coordinated by veanions with an [8] compareswell with the average U Oeq bond average Na3 Obondlength of 2.398 A Ê . lengthof 2. 47(12)A Ê derivedfrom numerous well-rened structures (Burns et al., 1997). The Structuralconnectiv ity structurecontains one symmetrically unique C 4+ cationin the usual triangular coordination, with Asis thecase with other known uranyl carbonates an average C Obondlength of 1.28A Ê (Table 4). withU:Cratioso f1:3,thestru ctureof Thereare three symmetricall ydistinctNa Na4(UO2)(CO3)3 containsthe uranyl tricarbonate cationsin the structur e.Na1 and Na2 are clustershown in Fig.1 a.Thecluster contains one octahedrallycoordinated by O atoms,with an UrO6 hexagonalbipyramid that shares three of its average Na1 Obondlength of 2.501(3)A Ê and an equatorialedges with CO 3 triangles.As for all
TABLE 4.Bond lengths (A Ê )andangles ( 8) for Na4(UO2)(CO3)3.
U1 O2 1.807(5) Na1 O3a,d,e,f,g,h 2.501(3)66 U1 O1 1.814(5) U1 O5a,b,c 2.385(4)63 Na2 O3h,k,a,e,l,m 2.444(3)66 U1 O4a,b,c 2.427(3)63 U1 Oeq> 2.41 Na3 O5n 2.286(4) O2 U1 O1 180 Na3 O3i 2.323(4) Na3 O4n 2.345(4) C1 O3j 1.236(7) Na3 O1 2.488(3) C1 O5f 1.310(7) Na3 O2o 2.547(4) C1 O4 1.284(6)
O3j C1 O4 124.2(5) O3j C1 O5f 122.6(5) O4 C1 O5f 113.2(5)
a = x + 1, x + y, z + Ý, b = y, x, z + Ý, c = x y + 1, y + 1, z + Ý; d = y +1, x y, z; e = y 1, x 1, z + Ý; f = x + y, x +1, z; g = x 1, y 1, z; h = x y, y +1, z + Ý; i = x + y + 1, x + 1, z; j = x 1, y, z; k = x + y, y 1, z Ý; l = x 1, x y, z Ý; m = y + 1, x + 1, z Ý; n = x + 1, y, z; o = y + 1, x + 1, z + Ý
300 CRYSTAL STRUCTURE OFN A4(UO2)(CO3)3
TABLE 5.Bond valence analysis* for Na 4(UO2)(CO3)3.
O1 O2 O3 O4 O5 S
U1 1.57 1.59 0.4763? 0.5163? 6.10 Na1 0.1566? 0.90 Na2 0.1866? 1.08 Na3 0.1663; 0.1363; 0.24 0.23 0.27 1.03 C1 1.54 1.35 1.27 4.16 S 2.05 1.98 2.11 2.05 2.05
*bond-valence parameters for U 6+ from Burns et al.(1997) and for other cations from Brese and O’Keeffe (1991)
knownstructures that contain the uranyl tricarbo- compositionCa 3f18.Thistrimer differs from the natecluster, these clusters are not directly linked Na3O11 trimer in Na4(UO2)(CO3)3 inthe coordi- butare connected through bonds to lower- valence nationof the cations and in the mode of cations.Burns et al. (1996)and Burns (1999) connectionof the polyhedra: shared vertices in thereforegrouped these structures with those that Ca3f18,incontrast to a sharededge in Na 3O11. containisolated clusters of polyhedra of higher However,the way that these trimers are linked bond-valence. withuranyl tricarbonate clusters to form hetero- Threesymmetrically related Na3O 5 polyhedra polyhedralsheets is similar in the two structures sharea commonedge, resulting in a trimerof (Figs 1c, 2a).In schro ¨ckingerite,the sheets are compositionNa 3O11 (Fig. 1b).Each trimer is linked to SO4 tetrahedraon oneside, and adjacent linkedto three uranyl tricarbonate clusters by sheetsare connected through hydrogen bonds to sharingequatorial edges of UrO6 hexagonal H2Ogroupsin the interlayers (Fig. 2 b). Note that bipyramidswith Na3O 5 polyhedra,resulting in a thestructure of schro¨ckingeriteis triclinic, but has heteropolyhedralsheet that is parallel to (001) apseudo-trigonalunit cell with parameters a = (Fig. 1c).Additionallinkages within the sheet are 9.634, b = 9.635, c = 14.391 AÊ , a = 91.41, b = providedby the sharing of avertexof the Na3O 5 92.33, g = 120.26(8). polyhedronwith a CO 3 triangle.Adjacent sheets TheXRD patternswere reported for two areconnected along [001 ];vertices common to all polymorphsof Na 4(UO2)(CO3)3 inthe Powder three Na3O5 polyhedrain the Na 3O11 trimer of DiffractionFile(In ternationalCenterfor onelayer correspond to uranyl ion O atomsof DiffractionData) .Thecalculated XRD pattern adjacentoffset sheets (Fig. 1 d). The Na1O6 and for Na4(UO2)(CO3)3 agreeswell with PDF Na2O6 octahedrashare faces, resulting in chains 11-0081,drawn from the work of Douglass ofoctahedra that extend along [001 ](Fig.1 e). (1956),but is signi cantly different from 13- Eachoctahedral vertex is shared with a CO 3 0038,suggesting that the compound we studied is triangleand a Na3O 5 polyhedron(Fig. 1 f,g). identicalto that prepared by Douglass (1956) .
Relatedstructures w ithU:C = 1:3 Na4 (UO2)(CO3)3 from theCzech Republ ic andChernoby l Thestructures of uranyl carbonate minerals are Asodiumuranyl carbonate mineral with the reviewedand illustrated in Burns (1999) .Of compositionNa 4(UO2)(CO3)3 wasfound at the these,the structure of Na 4(UO2)(CO3)3 is most Jachymovore district, Czech Public (Ondrus et closelyrela tedto that of schr o¨ckingerite, al.,1997),but the structure has not been reported NaCa3[(UO2)(CO3)3 ](SO4)F(H2O)10, which anda completedescription of themineral has not containsa heteropolyhedrallayer that is similar yetappeared. Based on powder diffraction data, tothelayer in Na 4(UO2)(CO3)3 (Mereiter,1986 a). bothtriclinic and trigonal unit cells (Table 1) Inschro ¨ckingerite,three symmetrically unique weregiven for the mineral (Ondrus et al., 1997); Caf7 polyhedra (f:unspecied ligand) link by itwas not possible to index all re ections using sharingthree vertice stoform a trimerof thecell of Douglass(1956) .Thematerial studied
301 YAPING LI ETAL.
(a) (b) (c)
Na3
Na3 Na3 a
a (d) (e)
Na1 Na3 c c Na2
asin120 asin120
(f) (g)
2B 2B
a a
O 2A O 2A
a a
FIG.1.The structure of Na 4(UO2)(CO3)3. (a)Uranyl tricarbonate cluster; ( b) Na33O11 trimer; (c)heteropolyhedral sheet formed by sharing corners and edges amoung uranyl tricarbonate clusters and Na3 3O11 trimers, projected onto (001); (d)the structure projected onto (010), Na1, Na2 and Care omitted; ( e)the structure projected onto (010); ( f) the structure projected onto (001), with Na(3) polyhedra omitted; ( g)the structure projected onto (001).The CO 3 groups are shown as black triangles, the UrO6 polyhedra are light grey, and the NaO n polyhedra are dark grey.
by Ondrus et al. (1997)was negrained. It is nuclearaccident in the Chernobyl No. 4 reactor. possiblethat some peaks in the diffraction pattern Alterationproducts collected from the Chernobyl aredue to impurities. The results of ourwork may ‘lava’ wereidenti ed by XRD andenergy providethe structure of theunnamed mineral. dispersivespectroscopy(EDS)as Uranylcarbonate phases have been identi ed Na4(UO2)(CO3)3,alongwith Na 3H(CO3)2 2H2O, onradioactive materials that resulted from the UO3 2H2O, Na2CO3 H2O, UO4 4H2O, and
302 CRYSTAL STRUCTURE OFN A4(UO2)(CO3)3 (a) Ca (b)
C U
C csina
S
bsina
asing asinb
FIG.2. The structure of schro¨ckingerite. ( a)Structure projected along [001];grey circles represent Nacations; ( b) structure projected along [010]; black circles represent H 2O groups.
UO2(CO3) (Burakov et al.,1999).Thephase we Clark, D.L., Hobart, D.E.and Neu, M.P.(1995) Actinide havestudied may be the same as one of the Na carbonate complexes and their importance in uranylcarbonates forming at Chernobyl. actinide environmental chemistry. Chem. Rev., 95, 25 48. Douglass, M. (1956) Tetrasodium uranyl tricarbonate, Acknowledgements Na4UO2(CO3)3. Anal. Chem., 28, 1635. Thisresearch was supported by the United States Finch, R.J., Cooper, M.A., Hawthorne, F.C.and Ewing, DepartmentofEnergyEnvironmental R.C.(1999) Renement of the crystal structure of ManagementScienc esProgra m(DE-FG07- rutherfordine. Canad. Mineral. , 37, 929 38. 97ER14820). Ginderow, D.and Cesbron, F.(1985) Structure de la roubaultite, Cu 2(UO2)3(CO3)2O2(OH)24(H2O). Acta Crystallogr. , C41, 654 7. References Grice, J.D. and Ferraris, G. (2000) Newminerals approved in 1999 by the commission on new Brese, N.E.and O ’Keeffe, M.O. (1991) Bond-valence minerals and mineral names, International parameters for solids. Acta Crystallogr. , B47, Mineralogical Association. Canad Mineral. , 38, 192 7. 245 50. Burakov, B.E., Strykanova, E.E.and Anderson, E.B. Li, Y., Burns, P.C.and Gault, R.A.(2000) Anew rare- (1999) Secondary uranium minerals on the surface of earth-element uranyl carbonate sheet in the structure Chernobyl ‘lava’. Mat. Res. Soc. Symp. Proc. , 465, of bijvoetite-(Y). Canad. Mineral. , 38, 153 62. 1309 11. Mandarino, J.A. (1999) Fleischer’sGlossary of Mineral Burns, P.C.(1999) Crystal chemistry of uranium. Pp. Species 1999 .The Mineralogical Record Inc., 23 90 in: Uranium: Mineralogy, Geochemistry and Tucson, AZ,USA. the Environment (P.C. Burns and R.J.Finch, editors). Mayer, H.and Mereiter, K.(1986) Synthetic bayleyite, Reviews in Mineralogy, 38.Mineralogical society of Mg2[(UO2)(CO3)3] 18(H2O): thermochemistry, crys- America, Washington, D.C. tallography and crystal structure. Tsch.Miner. Petr. Burns, P.C.,Ewing, R.C.and Hawthorne, F.C.(1997) Mitt., 35, 133 46. The crystal chemistry of hexavalent uranium: Mereiter, K. (1982) The crystal structure of liebigite,
polyhedron geometries, bond-valence parameters, Ca2UO2(CO3)3 ~ 11H2O. Tsch. Miner.Petr. Mitt. , and polymerization of polyhedra. Canad.Mineral. , 30, 277 88. 35, 1551 70. Mereiter, K.(1986 a)Crystal structure and crystal- Burns, P.C.,Miller, M.L. and Ewing, R.C.(1996) U 6+ lographic properties of aschro¨ckingerite from minerals and inorganic phases: acomparison and Joachimsthal. Tsch.Miner.Petr. Mitt. , 35, 1 18. hierarchy of crystal structures. Canad.Mineral., 34, Mereiter,K.(1986 b)Syntheticswartzite,
845 80. CaMg[(UO2)(CO3)3] 12H2O,and its strontium
303 YAPING LI ETAL.
analogue, SrMg[(UO 2)(CO3)3] 12H2O:crystallogra - Hlousek, J., Fryda, J.,Vavrin, I., Cejka, J.and phy and crystal structures. Neues Jahrb.Mineral., Gabasova, A.(1997) Newnaturally occurring phases Mh., 481 92. of secondary origin from Jachymov (Joachimsthal) . Mereiter, K.(1986 c)Neue Kristallographische Daten J. Czech Geol. Soc. , 42, 77 108. ueber das uranmineral andersonit. Anz. Oesterr Akad. Wiss. Math-Naturwiss , K13, 39 41. [Manuscript received 19 July 2000: Ondrus, P., Veselovsky, F., Skala, R., Cisarova, I., revised 8January 2001 ]
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