Cialdi, Corazza, Sabelli: La struttura cristallina della kernite, Na2B4O6(OH)2·3 H2O

Cialdi, Gloria and Corazza, Egizio and Sabelli, Cesare:
La struttura cristallina della kernite, Na₂B₄O₆(OH)₂·3 H₂O
Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Serie 8 42 (1967), fasc. n.2, p. 236-251, (Italian)
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The crystal structure of kernite, Na₂B₄O₆(OH)₂·3 H₂O has been determined by means of x-ray diffraction, using the Weissenberg equiinclination technique. The structure was solved from direct methods, giving the signs to 25% of the observed structure factors, and from a three-dimensional Fourier synthesis. Least squares refinement with 951 independent reflections yielded a reliability index of 0.083, based on the observed reflections only. The approximate positions of the hydrogen atoms could be deduced from stereochemical considerations. The monoclinic cell has dimensions, a = 7.022, b = 9.151, c = 15.676 Å; ß = 108.8°. The space group is P 21/c. For a cell containing four units of Na₂B₄O₆(OH)₂·3 H₂O, the calculated density is 1.904 g·cm^-3. The atoms within the square brackets are interconnected along the y axis so as to form an infinite chain complex [B₄O₆(OH)₂]_n^-2n. Both sodium atoms coordinate five oxygens according to a distorted trigonal bipyramid. The Na(1) and Na(2) coordination polyhedra are connected by a corner, and Na(1) shares an edge with its centro-symmetrical one, to form a four-membered group. The boron-oxygen chains, two per cell, are linked three-dimensionally by the Na polyhedra groups and by hydrogen bonds.

Referenze Bibliografiche

[1] J. GARRIDO, Symmetrie und raumgruppe des Kernits (Na₂B₄O₇·4 H₂O), «Zeit, für Krist.», LXXXII, 468 (1932).

[2] W. MINDER, Über den Bau einiger Hydrate von Natriumdiborat, «Zeit, für Krist.», XCII, 301 (1935).

[3] J. L. AMOROS, Nota sobre la macla (011) de la Kernita, «Estudios Geològicos», VII, 21 (1947).

[4] G. L. CHRIST e M. N. GARRELS, Relations among sodium Borate hydrates at the Kramer deposit, Boron, California, «Am. Jour. Sci.», 257, 516 (1959).

[5] P. J. BRAY, J. O. EDWARDS, J. G. O'KEEFE, V. F. ROSS e I. TATSUZAKI, Nuclear magnetic resonance studies of B11 in crystalline borates, «Jour. Chem. Phys.», 35, 435 (1961).

[6] H. E. PETCH, K. S. PENNINGTON e J. D. CUTHBERT, On Christ's postulated boron-oxygen polyions in some hydrated borates of unknown crystal structures, «Am. Min.», 47, 401 (1962).

[7] V. ROSS e J. O. EDWARDS, On the crystal structure of kernite, Na₂B₄O₇·4 H₂O, «Acta Cryst.», 12, 258 (1959).

[8] M. M. WOOLFSON, Direct methods in crystallography, Clarendon Press, Oxford (1961). | MR 129416 | Zbl 0129.46202

[9] D. D. CROMER e J. T. WABER, Scattering factors computed from relativistic Dirac-Slater wave functions, «Acta Cryst.», 18, 104 (1965).

[10] International Tables for x-ray crystallography, Vol. III, Kynoch Press, Birmingham (1962).

[11] V. ALBANO, P. L. BELLON, F. POMPA e V. SCATTURIN, Programmi cristallografici per l'elaboratore I.B.M. 1620. Nota IV: Affinamento di una struttura cristallina col metodo dei minimi quadrati, «Ric. Sci.», 3 A, 1067 (1963).

[12] D. W. I. CRUIKSHANK, D. E. PILLING, A. BUJOSA, F. M. LOVELL e M. R. TRUTER, Crystallographic calculations on the Ferranti Pegasus and Mark I computer. In: Computing methods and the phase problem in x-ray crystal analysis, Pergamon Press, London 32 (1961).

[13] C. L. CHRIST, Crystal chemistry and systematic classification of hydrated borate minerals, «Am. Min.», 45, 334 (1960).

[14] C. TENNYSON, Eine systematic der Borate auf Kristallchemischer grundlage, «Fortschr. Miner.», 41, 64 (1963).

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Referenze Bibliografiche