X-ray crystallographic studies on β-ZrF4

2038

Notes

J. Inorg. Nucl. Chem., 1964, Vol. 26, pp. 2038 to 2039. Pergamon Press Ltd. Printed in Northern Ireland

X-Ray crystallographic studies on [~-ZrF4 (Received 11 May 1964; in revised form 17 June 1964) THE FORMATIONof fl-ZrF4 during the decomposition of (NH4)a ZrF7 was established by CHERETIEN and GAUDe,~AUin 1958, the X-ray powder pattern being radically different from that of ~-ZrF4. c1~ The unit cell and space group of the fl-ZrF4 has not so far been reported and hence a systematic study of the powder and single crystal data were undertaken. TABLE 1

d(/~)

6.87 6.06 4"75 3"88 3"63 3"43 3'27 3'09 3"01 2"57 2-37 1"95 1"90 1.88 1"84 1.79 1.59 1"57 1"51 1"43 1.39 1.35 1-14

Pseudo orthorhombic cell

monoclinic cell

hkl

hkl

020 002 200 220 032 040 222 203 213 233 400 163 315 433 344 271 435 601 066 641 554 701 656

020 20~ 202 222 23] 040 420 50151T 53T 404 46] 81~ 731 74T 371 93T 705 66~ 745 951 806 1250

I

W V.W V.W S M V.S M M V.S V.V.W V.V.W W M W S W V.V.W S W W W M W

The powder data were obtained on Phillips wide angle goniometer using filtered copper radiation; single crystal data were obtained from rotation and Weissenberg techniques using filtered copper and molybdenum radiations. Almost all crystals were severely twinned. One small fragment was finally chosen for X-ray work and, as revealed by X-ray photographs, this too was not free from twinning and accurate cell parameters could not be obtained from Weissenberg photographs. The final values were therefore computed from powder data. It was found by Ito's method that the powder lines could be indexed as orthorhombic with cell parameters a = 9"49 b = 13'73 and c = 12-12 A. ortho

ortho

ortho

(see Table 1). This cell is found to contain twenty-six formula units. (PobB = 4.544, Peal of ~-ZrF4 4.568 g. cm-3). Single crystal work, however, revealed that the true cell is monoclinic and the orthorhombic one is a pseudo cell. tl~ A. CHERETIENand B. GAUDREAU,C.R. Acad. Sci. Paris. 15, 2266 (1958).

Notes

2039

Zero a n d higher layer W e i s s e n b e r g p h o t o g r a p h s with the crystal rotating along the a a n d b axes were obtained. T h e cell p a r a m e t e r s are, a = 15.8

b ~ 13-7

c -- 15"1 ~

T h e n u m b e r o f molecules in this cell is Z = 52. T h e o d d a n d hence the space g r o u p is P21 or P21/.... This cell c a n be easily related. T h e t r a n s f o r m a t i o n f r o m matrix, 1 0 o 1 I 0

and

fl -- 107'.

only s y s t e m a t i c absences are 0k0, when k is m o n o c l i n i c cell a n d the p s e u d o o r t h o r h o m b i c o r t h o r h o m b i c to monoclinic is by the Niggli 1 0 T

T h e p o w d e r d a t a were reindexed on the basis o f the true monoclinic cell (Table I) a n d a better value of t h e cell p a r a m e t e r s obtained as follows a = 15.82

b = 13"73

e -- 15.11 A

and

fl -- 106 ° 15'

T h e m o n o c l i n i c angle o f t h e p s e u d o o r t h o r h o m b i c cell is f o u n d to be 90 ° 7'. There does n o t seem to be a n y structural relation between the ~- a n d fl-phases except t h a t the c axis is nearly doubled.

Acknowledgement--We t h a n k

D r . J. SHANKAR for his keen interest a n d D r A. CHERETIEN for providing u s with the p u r e sample o f fl-ZrF~.

Chemistry Division Atomic Energy Establishment Trombay Bombay

V. AMIRTHALINGAM K.V.

MURAL[DHARAN