May, 1950 [CONTRIBUTION FROM THE
THECRYSTAL STRUCTURE OF SODIUM SUPEROXIDE DEPARTMENT OF
CHEMISTRY AND CHEMICAL ENGINEERING AND UNIVERSITY O F CALIFORNIA]
2251
RADIATION LABORATORY,
The Crystal Structure of Sodium Superoxide' BY D. H. TEMPLETON AND CAROL H. DAUBEN The superoxides of potassium, rubidium and 5.490 * 0.005 A.) whose relative intensity correcesium (KOz, etc.) are readily prepared by reaction sponded with the degree of yellow color. The relaof the elements and have long been known2 The tive intensity also corresponded to the NaOz concorresponding compound of sodium has only re- tent reported for each sample,4 except in some cently been prepared in a reasonably pure state cases where light color indicated exposure to moisby the reaction of sodium peroxide (the highest ture. Exposure of yellow samples to moist air caused oxide ordinarily obtained j with oxygen a t approximately 500' and 300 atmospheres pressure. K;e them rapidly to become white and destroyed the have determined the crystal structure of this com- cubic phase. I n a sample containing 707; NaOz only the lines of the cubic phase were observed. pound from X-ray powder diffraction pattern^.^ The crystal structures of KOz, RbO2 and CsOn In all other samples, various complicated patterns are known to be isomorphous with calcium car- were also present. From these observations we bide.6 I n this structure a face-centered tetrago- deduce that the cubic phase corresponds to sodium nal (pseudocubic) lattice of metal ions is interpene- superoxide. We cannot exclude on this basis the trated by a similar face-centered lattice of 0,- possibility that a solid solution range exists corions, to form a distorted NaCl structure. Each responding to less oxygen than the ideal Na02. pair of oxygen atoms is oriented with the 0-0 However, the excellent agreement of observed and bond parallel to the tetragonal c axis, and conse- calculated intensities noted below makes it unquently c is somewhat greater than a, as listed in likely that a large defect in oxygen content exists. Table I. The existence of 0 2 - ions is demonNOTEADDED IN PROOF:-ReCent examination of some strated by the X-ray studies and is in agreement mixtures of NazOz and NaOz prepared under more anhywith magnetic measurements which indicate one drous conditions by Professor P. W. Gilles of the University of Kansas shows that the solid solubility is not extensive unpaired electron for each two oxygen atoms6 a t room temperature. Both phases were clearly observed in samples of 9 and 94 weight % NaOp. We estimate TABLE I from the relative intensities of the patterns of the two phases UNIT CELLDIMENSIONS OF ALKALISUPEROXIDES that the two-phase region must extend a t least from 5 to 97% NaOp. Compound a , A. c, A. p x , g. cm. - 8
NaO? 5.49 .. 2.21 KO," 3.71 6.76 2.14 RbOy" 6.01 7.04 3.07 CsOn" 6.29 7.28 3.80 a Ilimensions of Helms and Klemm, Z. aitorg. aligem. Chcm., 241, 97 (1939), are multiplied by the factor 1.0020 to correct to the basis CUKLV~ = 1.5405 A. The densities are recalculated from the resulting numbers.
The samples were received in Pyrex capillaries as mixtures of sodium peroxide, sodium superoxide, and hydration products, ranging in color from bright yellow to white. Powder diffraction picX-rays (filtered with tures taken with copper KCY nickel) showed a face-centered cubic phase (a = (1) PresenLed before the Division of Physical and Inorganic Chemistry a t the Atlantic City Meeting of the American Chemical Society, September 23, 1949. (2) (a) A. V. Harcourt. J . Chzm. SOC.,14, 267 (1862); (b) W. Holt and W. E. Sims. ibid., 66, 432 (1894); ( c ) E. Rengade, A n n . chim. $hys., (8) 11, 348 (1907). (3) S. E. Stephanou, W. H. Schechter, W. J. Argersinger and J. Kleinberg, THIS JOURNAL. '71, 1819 (1949). (4) We are indebted t o Dr. S. E. Stephanou and Professor Jacob Kleinberg of the University of Kansas for a number of samples containing sodium superoxide in various amounts, and for analytical d a t a concerning these samples. (5) (a) W. Kassatoschkin and W. Kotow, J. Chcm. Phys., 4, 458 (1936); (b) A. Helms, 2. angcw. Chcm., 61, 498 (1938); (c) A. Helms and W. Klemm, 2. anorg. allgcm. Chcm., 241, 97 (1939); C11-type, Slruklurbcrichl, I, 740 (1931). (6) (a) E. W. Neuman, J. Chcm. Phrs., 2 , 31 (1934); (b) W. Klemm and H. Sodomann, 2 . anorg. allgcm. Chcm., 116, 273 (1935).
Disordered Structures.-The intensities of the lines of the NaOz phasc were estimated by
TABLE I1 OBSERVEDAND CALCULATED INTENSITIES FOR DISORDERBD STRUCTURES h kl
111 200 220 311 222 400 33 1 420 422 333 511
440 531 442 600
obs.
-
2.
(Rota-
1. (zoo)'' tion) 3. ( X X X ) ~4. 0.119 n = 0.119 z = 0.072 iz
x
