thorium compound, is crystallization water. This is probably the reason for the difference in the symmetry of crystals of these compounds; in other respects they are very similar. This difference can probably find an explanation in the eiectron structure of Th and U. All the calculation work was performed in the Mathematical Division of the ICP of the Academy of Sciences of the USSR using programs developed there. We would like to thank L. E. Maksimova, Z. I. Safina, V. I. Andrianov, and B. L. Tamopol'skii.

THE

BINARY O X I D E S OF U R A N I U M , V.

K. T r u n o v ,

Yu.

TANTALUM,

P. S i m a n o v ,

and

L. M.

A N D TIN Kovba

M. V. Lomonosov Moscow State University Translated from Zhurnal Strukturnoi Khimti, Vol. 4, No. 2, pp. 277-279, March-April, 1963 Original article submitted March 14, 1962

The binary oxides of uranium, tantalum, and tin were studied in a number of papers [1-4]. UO z and SnO, do not form compounds [4]. Gasperin [1-3] gave data on binary oxides of Ta and Sn, and also U and Ta, which differ from our results. We have studied the binary oxides of U, Ta and Sn. Mixtures of stoichiometrtc amounts of the initial oxides were roasted at temperatures from 1200 to 1800 ~ The specimens were photographed with CuK a radiation (Guinier focusing camera with a curved single crystal of germanium as the monochromator [5]). The results of the x-ray phase analysis of the roasted specimens are given in Table 1. TABLE 1. Results of X-Ray Phase Anal Composition of initial preparation UO 2 + TazOs UO z + 2Taro s U3Os + 3Ta205 UTa3Olo.~ + UTaOs. n The same w

ii

n

n

w

H

2SnO + Ta~:) s 3SnO + Ta20 s SnO + TazO s SnO + 2Tang:)s SnTa,lOn SnO~+ Taw~Os ( S n : T a = 2 : 1 , 1 : 1 . 1:2) NO s + SnO~(W:Sn = 2 : 1 , 1 : 1 , 1 : 2 )

SiS

Treatment N 2, 1800 ~ The same 1100~ NO~., 350 ~ H~, 400 ~ Hz, 500 ~ H~, 600 ~ H2, 700 ~ Hz, 1000 ~ Vacuum, 1000 ~ The same

N O m 500 ~

1100-1200 ~ The same

Phases found UO~ + U(TaOs) 4 U(TaOs)4 UTa~Olo.n+ UTaOs. 1T UTasOlo.rt, Tang:)6, UOs UTasOio.n + UTaOs. n + Ta~,O s

UTa~O10.x7 + Ta20 s The same U(TaOs)4, UO2, Taro s Sn2Ta~z SnsTax,Os SnzTa:,O7 + SnTad911 SnTa4Otl SnTa40 u SnOz + Ta~Os WOs + SnO2

When investigating binary oxides of uranium and tantalum, Gasperin found two compounds: UTazO 7 (pyrochlore type) and UTa~O 8, structurally similar to UsOs. Our results were quite different. As can be seen fromTable 1, the spec i m e n of composition UTazOT(UO 2 + TazOs) was two-phase. During the roasting of UOz and Ta2Os taken in a ratio U : Ta = 1 : 4 the compound U(TaOs)4 is formed. We can therefore assume that the system UO2- Ta2Os does not contain the compound UTazO 7 since with a ratio U : Ta = 1 : 2 the specimen contains UO2 and U(TaOs) 4. The x-ray pattern of a = 7.720, 0.003 and c = 3.860i 0.002 kX.

252

During the roasting of U~:)8 and Ta~O s with a ratio U : Ta = 1 : 2 (UTa~OT.s0 a mixture of two phases is formed rhombie and hexagonal. As can be seen from Table 1, an a t t e m p t to oxidize a specimen of composition U T a ~ 7 . s 7 to UTa208 in a current of NO 2 at 350 ~ did not produce the desired result, although the mixed oxide of uranium is oxldized to the trioxide under these conditions. The x - r a y pattern of the oxidized specimen has lines of three phases: hexagonal, Ta~,Os, and one of the modifications of UO 8. After reduction of specimens with composition UTa~Ov.s7 by hydrogen at 400, 500, 600, 700 and 1000 ~ there is a regular increase in the amount of the hexagonal phase and Ta~O s lines appear on the x - r a y patterns of these specimens. On the x - r a y pattern of a specimen reduced at 1000 ~ there are lines of IX) z, Ta~O 5 and U(TaOs) 4, The a b o v e - m e n t i o n e d hexagonal and rhombic phases were obtained in the individual state. The hexagonal phase is formed with a ratio U : Ta = 1 : 3 (UTa3010AT) and the rhombie phase is formed with a ratio U : Ta = 1 : 1 (UTaO~.17). The x - r a y pattern of the compound UTa~::)x0.17 is indexed on the assumption of a hexagonal unit cell with a = 7,389~ 0.003 and c = 15.77~0.02 kX; N = 4. The results for the indexing o f the x - r a y patterns of UTa3OIsA7 are given in Table 2. TABLE 2. Results for the Indexing of X-Ray Patterns of UTag310.z 7 UTa,O. [31

It

d. k X

lO'/d m

iOVdc

hkl

d, kX

1/2 1/2 iO 1/~ t0

1/4 I/g 9 1/4 1/2 1/2 1 1/g 3

1/2 6 4 5

t 4 4

5,936 4,969 4,t)69 3,947 3,354 3,200 3,140 3,025 2,486 2,4t9 2,390 2,3t4 2,198 2,124 i,9706 t,9247 t,8459 t,6794 t,6720 t,6482 t,5997 t,4826

285

101 102 t03 0O4 644 888, 894 104, t12 977 200 t0t7 201 1095 1t3 t621 204 210 t750 211 1871 212 2072 213 2215 107 2574 0O8 2704 t17 2932 220 3557 208 3575 224 2t7 3681 4O0 3909 4552 404

av.

3,94

v,c,

3,20

c,

2,49

av.

t,978

av, c,

1,855 1,676

av. av.

t,607 1,487

It can be assumed that the compound UTazO10AT is structurally Similar to the compound UV3010 prepared by Wang Shih-hua [6]. The intensive lines of the UTaOs.17 x - r a y pattern are indexed on the assumption of a rhombic (pseudohexagonal) subcell with a = 6.450, b = 3.772 and c = 3.972 kX. The presence of superstructural lines points t o t h e ordered arrangement of U and Ta atoms. Comparing the interplanar spacings for intensive lines of the UTa3OI0.17 x - r a y pattern and the interplanar spacings given by Gasperin for UTa2~Os (Table 2) and also taking into account the facts mentioned above, we can conclude that Gasperin had taken the compound UTasO10ol 7 for the compound UTazO s. We have also studied the systems SnOz-TazO s, SnOz-WO s, S n O - T a z O 5, SnO~-WO 2. In the systems SnOz-TazO s and SnOz-WO s at temperatures up to 1200" no compounds were detected. In the system SnO-Ta~X)5 we established the existence of a variable composition phase 2SnO. TazO6-3SnO. TazO s with a pyrochlore structure and unit c e l l parameter a = 10.542~:0.003 kX for the composition SnzTazO 7 and a = 10.586 0.003 kX for the composition SnaTa20 a. With a high content o f Ta20 5 a phase is formed which is close in composition to SnTa4Oll. Since Gasporin mentions the existence of a compound SnTa4Ot2, which is not formed by direct roasting of SnO 2 and Ta~O~ at temperatures up to 1100 ~ (at higher temperatures SnO z has increased v o l a t i l i t y ) we tried to oxidize

253

SnTaaO u to the composition SnTa431z. The oxidation was accomplished by prolonged roasting at 800* and in a current of NO2 at 500". Oxidation does not lead to a noticeable increase in weight of the initial specimens. The x-ray patterns of specimens before and after oxidation are identical. SnOz and WO2 form the compound SnWO4. 1. 2. 3. 4. 5. 6.

LITERATURE CITED M. Gasperin, Compt. rend, 243, 1534 (1956). M. Gasperin, Compt. rend. 244_.__,1295 (1957). M. Gasperin, Bull. soc. franc, mineral, et eryst. 838, 1 (1960). S.M. Lang, F. P. Knudsen, C. Z. Fillmor, and P.. S. Ruth, Natl. Bur. Stand. USA, circ. 566 (1956). Yu. P. Simanov, V. K. Trunov et al., Zavodskaya laboratoriya (in press, 1963). Wang Shih-hua, L. M, Kovba, and V. I. Spitsyn, Zh. strukt, khimtt (in press, 1963).

A PROGRAM FOR THE C A L C U L A T I O N OF S T R U C T U R E AMPLITUDES WITH I S O T R O P I C THERMAL PARAMETERS FOR A LARGE E L E C T R O N I C C O M P U T E R F. A. B r u s e n t s e v Institute of Inorganic Chemistry, Siberian Division, Academy of Sciences. USSR, Novosibirsk Translated from Zhurnal Strukturnoi Khimii, Vot. 4. No. 2, pp. 279-281, March-April, 1963 Original article submitted July 2, 1962

In the search for theoretical structure amplitudes most of the computer work is expended in calculating the trigonometrical part of the structure factor and the value of the atomic function fj 0akl) as a function of the indices (h, k, !). The atomic functions are usually given by a table with an interval of 0.1 or 0.05 with respect to s = sin 0/9,. The intermediate values are found by linear or quadratic interpolation. Linear interpolation from the tabular data usually gives two correct significant figures of the quantity fj (hk/). In order to reduce the ingoing information some authors use an analytical representation of the structure factor [1, 2]. In most cases sin x and cos x for the trigonometrical part of the structure factor are calculated by means of appropriate standard subprograms, which is very time-consuming. In this sense it is more desirable to select sin x and cos x from an appropriate table or to compile a special subprogram to calculate them with less accuracy, sufficient only for the tasks of structure analysis of the crystals. Many Soviet and other papers deal with the programing of the calculation of structure amplitudes. Sparks, Prosen [3] and then Ahmed and Barnes [4] described general programs for the calculation of structure amplitudes. In the Soviet literature this problem is dealt with by Levtn and Porai-Koshits [5], Trifonov and Shchedrin [6], and other authors [7, 8]. The authors of [1, 2, 11] considered a method to allow for the anisotropic thermal parameters of atoms tn the calculation of structure amplitudes. The authors of [9-12] described programs for the calculation of structure amplitudes with anisotropic thermal parameters. We compiled a program for the calculation of structure amplitudes for the steric case with an allowance for the individual lsotropic thermal parameters of the atoms from the formula N'

F

(hkl) = E (i/Kj) [je --Bj (slnOIX)'T j,

(1)

where N is the number of atoms in the independent part'of the unit cell of the crystal, fj is the atomic function of the j_th atom, Tj is the trigonometrical part of the strueture factor.

254