Structure types of potassium and rubidium molybdate and tungstate at elevated temperatures

Structure types of potassium and rubidium molybdate and

tungstate at elevated temperatures

Citation for published version (APA):

van den Akker, A. W. M., Koster, A. S., & Rieck, G. D. (1970). Structure types of potassium and rubidium

molybdate and tungstate at elevated temperatures. Journal of Applied Crystallography, 3(Pt. 5), 389-392.

https://doi.org/10.1107/S0021889870006477

DOI:

10.1107/S0021889870006477

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Published: 01/01/1970

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). Appl. Cryst. (1970). 3, 389

Structure Types

of

Potassium

and Rubidium

Molybdate

and

Tungstate at

Elevated

Temperatures

BY A.W.M. VAN DEN AKKER, A.S.KOSTER AND G. D. RIECK

Laboratory of Physical Chemistry, Technical University, Eindhoven, The Netherlands

(Received 23 March 1970)

The isomorphisms and the transition points of K2Mo04, K 2W04, Rb2M004 and Rb2W04 were studied and the cell constants of the occurring phases computed.

Introduction Experimental

389

During an investigation of the structures of the normal alkali molybdates A2Mo04 and tungstates A2W04, it

was found that there is considerable disagreement

among various authors concerning the number of

phases found at elevated temperatures and the tempe -ratures at which the transformations occur. Here we report results of our high-temperature X-ray work on

the potassium and rubidium salts.

Powder X-ray diffraction patterns were made from samples made and checked for purity by Kools, Koster

& Rieck (1970). The powders were mixed with Vaseline and distributed uniformly over a fiat sample holder. A Nonius high-temperature focusing Guinier camera

was used. The sample holder, consisting of a gauze of

Pt-10%Rh wires, was submitted to programmed heat -ing. The rate of heating from room temperature up to

Table 1. Modifications and cell constants (A) The standard deviations in the last decimal are in parentheses. Molybdate

Potassium < 305°C Monoclinic, space group C2/m, K2Mo04 type (1).

25°C: a= 12·348 (3), b=6·08l (2), c=7·538 (2)

A

; P=

ll5·74 (5)0

• [(f) is in agreement with (Ill).] 305-440°C Related to P-K2S04 type. 36o•c: a=6·30, b= 10·92, c=7·95

A.

Possibly doubling of b and c.* > 44o•c Hexagonal, space group P!ml,

cx-K2S04 type (this work). 480°C: a=6·33! (5), c=8·07 (I)

A

(this work).

Rubidium < 23o•c Monoclinic, space group C2/m, K2Mo04 type (III).

25•C: a=l2·821(2), b=6·253 (I),

c=?-842 (I) A; P=ll5·64 (1)0 (III). 230-500°C Orthorhombic, space group

Pmcn, P-K2S04 type (Ill). 31o•c: a=6·460 (6), b=l 1·27 (1),

c = 8·185 (5)

A

(this work).

> 500°C Hexagonal, space group P3"m!, a-K2S04 type (this work). 52o•c: a=6·54l (6), c=8·445 (8)

A

(this work).

(I) Gatehouse & Leverett (1969). (ll) Koster, Kools & Rieck (I 969). (HI) Kools, Koster & Rieck (1970).

• See text.

i'

See text.

Tungstate

< 370°C Monoclinic, space group C2/m, K2Mo04 type (lJ).

25°C: a= 12·380 (2), b=6·117 (1), c=7·554 (I) A;

P=

I 15·96 (W. 370-435 •c Related to P-K2S04 type. 395°C: a=6·35, b=li·OO, c=8·03 A.

Possibly doubling of b. • > 435 •c Hexagonal, space group P!m I,

a-K2S04 type (this work). 485°C: a=6·365 (5), c=8·07 (l) A

(this work).

< 295 •c Monoclinic, space group C2/m, KzMo04 type (III).

25•c: 12-841 (2), b=6·285 (l),

c=7-854 (!)A;

P=

115-82 (1)0 _(Ill). 295-390°C Orthorhombic, space group

Pmcn, P-K2S04 type (lll). 345°C: a=6·506 (6), b=11·34 (1),

c=8·219 (5)

A

(this work). 390-465°C Related to P-K2S04 type 435°C: a=6·56, b= I 1·35, c=8·30 A.t

> 465

•

c

Hexagonal, space group P3"m1, a-K2S04 type (this work). 495•c : a=6·568 (6), c=8·411 (8)

A

390 STRUCTURE TYPES OF POTASSIUM AND RUBIDIUM MOLYBDATE Table 2. Transition temperatures of the compounds (in

o

q

K2Mo04 Van Klooster (1914) 327 Hoermann (1929) 323 Schmitz-Dumont (1951) 321 Caillet ( 1967) 323 This wqrk 305 KzW04 Van Klooster (1914) 388 Van Liempt (1922) 351-358 Hoermann (1929) 338 Schmitz-Dumont (1951) 370 Caillet (1967) 370 This work 370 RbzMo04 Schmitz-Dumont (1951) Salmon (1969) This work 230 RbzW04 Spitzyn (1947) Salmon (1 969) This work 295

about 600°C and cooling down was about l0°C.hr-1_. Under these circumstances, using a calibrated

thermo-couple, the estimated error of the temperatures given is about

±

10°C.

The calibration for diffraction angles was carried out

with a sample of quartz. Cu Ka radiation was used and calculations were carried out with the average a1a2 value of -1.=1·5418

A.

Cell constants were obtained by a least-squares method minimizing L_(l/d~bs-l/d~₁₀)2_•

Results

Table l lists tlv~ compounds, the temperature ranges of stability, and, if known, structure type and cell constants at a temperature within the concerned s ta-bility range.

In three cases the structure type could not be

deter-mined with certainty. Most of the lines of the potassium salt phases marked by an asterisk can be indexed on the basis of an orthorhombic structure (f3-K2

S0

4 type);

some weak lines, however, can only be indexed, though not very reliably, after doubling the mentioned axes (axis). Most of the lines of the rubidium tungstate phase marked by a dagger can be indexed on the ba -sis of an orthorhombic structure (f3-K2

S0

4 type); compared with the underlying orthorhombic phase,

however, some weak Jines have disappeared and some

new ones have appeared; doubling of any of the axes gives no possibility to complete indexing.

In Table 2 the transition temperatures found by us are listed together with values from literature.

All transitions are reversible without delay except

those from the orthorhombic to the monoclinic form

of the rubidium compounds, which are extremely sluggish, and those from the

fl-

K2

S

0

4 type related st ruc-ture to the monoclinic structure of the potassium

salts, which are reversible with a slight delay.

454 479 458 480 439 475 438 462,480 440 455 435 552 512 500 500-502 515-517 466 518 390 465

Tables of indexed reflexions of the hexagonal struc

-tures and of the orthorhombic rubidium compound structures are given in Table 3.

Table 3. Observed spacings (A), relative intensities and indices

(a) Potassium molybdate, K2Mo04 at 480•c.

Hexagonal; space group P1ml. Stability range > 440•c. a=6·331 (5), c=8·07 (I)

A.

d 1/lt 5-490

A

40 4·542 100 4·038 30 3·252 80 3·171 90 2·742 10 2·595 5 2·491 20 2·416 10 2·268 30 2·018 5 2·007 15 1·9192 5 1·8435 15 1·8281 15 1·7013 10 1 ·6648 5 1·6422 5 1·5825 10 1·4945 3 1·4734 3 1·4229 3 hkl 100 101 002 102 110 200 201 112 103 202 004 211 203 212 300 114 302 213 220 311 222 312 20obs 16·13 19·53 21·99 27·41 28·12 32·63 34·53 36·03 37·19 39·71 44·88 45·13 47·32 49·39 49·84 53-84 55·12 55·94 58·25 62·05 63·04 65·55 20colc 16·15 19·56 22·01 27-42 28·17 32·64 34·52 36·03 37·20 39·71 44·88 45·13 47·30 49·40 49·85 53·83 55·12 55·96 58·24 62·05 63·03 65·54 i/20 - 0·02 - 0·03 - 0·02 - 0·01 - 0·05 - 0·01 +0·01 0·00 - 0·01 0·00 0·00 0·00 +0·02 - 0·01 - 0·01 +0·01 0·00 - 0·02 +0·01 0·00 +0·01 +0·01

(b) Rubidium molybdate, Rb2Mo04 at 3to•c. Orthorhombic; space group Pmcn.

Stability range 230-5oo•c. a=6·460 (6), b = 11·27 (1), c=8·185 (5)

A.

d 5-630

A

4·630 4·095 3·848 /fit JO 40 20 5 hkl 020+ 110 021 +Ill 002 012 1120 + 0·02/- 0·06 +0·05/-0·02 - 0·02 - 0·01 d J-7 H. J-4' 3-3 3-2• 2·91 1·8 2·81 2·71 2-6 2-5> H 2·41 2-4 2·3· 2·3 2·3 H 2·1 2·1 2·1 2·1 2·0 2·0 1·9 1·9 1·9 1·9 1·8 1·8 1·8 1·8 1·8 1·8 1·7 1·/ 1·/ 1·7 H 1·6 I·~ H I·! (c) 5·( 4·· 4-: 3< 3< 2·1 2·: 2·· 2·' 2· 2·1

1

·

:

1·: I·' 1· 1· 1· I· I· I· I·

A. W. M. VAN DEN AKKER, A. S. KOSTER AND G. D. RIECK 391

Table 3

(cont.)

Table 3

(cont.)

d I/ II hkl L118 d 1/11 hkl L118 ]-770 5 121 0·00 1·2932 2 224+ 116 - 0·03/- 0·04 3·457 20 102 0·01 1·2354 2 410 +0·04 J-416 5 031 - 0·02 3·310 80 022+112 +0·01/-0·04 )-241 100 130+200 (d) Potassium tungstate, K2W04 at 48s•c.

2·946 10 122 +0·01 Hexagonal; space group pjml. Stability range > 435 •c.

2-818 5 040 0·00 a=6·365 (5), c=8·07 (1)

A.

2·801 5 220 +0·03 _{d I III hkl L128} 2·768 15 032 -0·01 2·652 10 221 +013 0·00 s·soo

A

70 100 +0·03 2·543 5 132 +0·01 4·555 100 101 -0·02 2·472 20 212 +0·03 4·031 40 002 +0·02 2·463 20 141 0·00 3·253 50 102 +0·03 2-453 20 023+ 113 +0·04/ 0·00 3·180 60 110 +0·02 2·346 5 231 +0·02 2·754 20 200 +0·03 2·321 10 042 -0·01 2-606 30 201 +0·02 2·311 50 222 +0·03 2·498 40 112 +0·01 2·207 3 033 +0·01 2·417 30 103 +0·01 2·184 3 142 0·00 2·275 30 202 +0·01 2·174 5 051 -0·01 2·082 10 210 +0·02 2·!29 3 150 -0·02 2·017 40 004+211 +0·01/0·00 2·101 15 232 +0·03 1·924 10 203 +0·03 2·046 15 004 0·00 1·851 20 212 0·00 2·015 3 014 -0·04 1·837 15 300 +0·01 1·973 3 052 0·00 1·704 10 114 0·00 1·9504 5 104 +0·01 1·672 10 302 -0·01 1·9218 5 024+ 114 + 0·04/ + 0·01 1·647 10 213 0·00 1·9042 5 302 +0·06 1·591 10 220 0·00 1·8854 5 242 -0·02 1·549 5 105 0·00 1·8772 20 060+ 143 + 0·03/- 0·04 1·529 5 310 -0·01 1·8664 20 330 +0·07 1·502 10 311 -0·01 1·8425 5 124 +0·02 1·481 5 222 -0·01 1·8211 3 331 +0·02 1·430 5 312 0·00 1·8030 5 251 +0·01 1·329 5 313 -0·01 1·7968 10 034 +0·01 1·304 5 402 -0·02 1·7607 5 161 +0·02 1·249 5 224+321 -0·01 1·7299 15 204+134 - 0·04/ + 0·05 1·203 5 410 +0·02 1·7080 10 062 - 0·03 1·6971 3 332 +0·10

1·6508 3 162 - 0·02 (e) Rubidium tungstate, Rb2W04 at 345•c.

1·6229 5 260 +0·04 Orthorhombic; space group Pmcn.

1·6125 5 070 -0·09 Stability range 295-39o•c.

1·5710 20 115+234 + 0·02/- 0·02 a=6·506 (6), b=11-34 (1), c=8·219 (5)

A.

d 1/ll hkl L128

(c) Rubidium molybdate, Rb2Mo04 at s2o•c. 5·661

A

15 020+ 110 + 0·02/- 0·04

Hexagonal; space group PjmJ. Stability range > 500 •c. 4·659 70 021 +111 + 0·03/- 0·02

a=6·541 (6), c=8·445 (8)

A.

4·110 25 002 +0·01 3-866 5 012 - 0·01 d !/II hkl L128 3·799 5 121 -0·03 5·675

A

10 100 - 0·03 3-474 10 102 +0·01 4·713 40 101 -0·04 3·326 100 022+ 112 + 0·01/- 0·03 4·225 30 002 -0·01 3·273 90 130 -0·04 3·390 90 102 - 0·04 3·252 50 200 +0·03 3·276 100 110 -0·06 2-964 5 122 0·00 2-834 5 200 -0·03 2-840 3 040 -0·06 2·586 10 112 - 0·01 2·822 5 220 +0·01 2·520 5 103 +0·01 2·783 10 032 -0·02 2·353 60 202 -0·01 2·681 3 041 -0·02 2·110 10 004 +0·03 2·668 3 013+221 - 0·06/ + 0·03 2·076 2 211 - 0·02 2·557 15 132 +0·01 1·9096 25 212 0·00 2·488 3 212 +0·04 1·8887 15 300 - 0·02 2·465 15 023+113 +0·03 1·7729 15 114 +0·02 2·359 3 231 +0·05 1·7237 10 302 -0·01 2·335 10 042 -0·03 1·7050 5 213 - 0·04 2·326 20 222 +0·01 1·6360 15 220 -0·03 2·111 5 232 +0·01 1·5247 5 222 0·00 2·071 5 151 +0·02 1·4723 10 312 0·00 2·055 5 004 -0·01 1·4069 5 304+006 +0·03/+ 0·02 1·8985 10 152 +0·01 1·3421 2 402 +0·03 1·8913 10 312 +0·03

392 STRUCTURE TYPES OF POTASSIUM AND RUBIDIUM MOLYBDATE Table 3 (cont.) d !fit hkl 1·8805 10 330 1·8511 3 124 1·8044 3 034+ 161 J ·7377 10 204 1·7179 5 214+062 1·7105 5 332 1·6862 5 153+243+341 1·6342 5 260 1·6263 5 015 1·5782 5 025 + 234 + II 5 L120 +0·04 +0·03 + 0·03/ + 0·01 0·00 -0·01/-0·03 +0·03 + 0·04/- 0·03/ + 0·0 I 0·00 0'03 + 0·02/ + 0·02/0·00 d 1·4767 1·4077 Table 3 (cont.) hkl 312 304 L120 +0·00 +0·03 (f) Rubidium tungstate, Rb2W04 at 495°C.

Caesium molybdate and tungstate, showing fl-K2S04

type orthorhombic structure at room temperature (Kools, Koster & Rieck (1970), are believed to have a

hexagonal o::-K2S04 arrangement at elevated tempera

-tures. This conclusion has been reached by visual com -parison of the high-temperature diffractographs with those of the potassium and rubidium compounds.

Hexagonal; space group P3"ml. Stability range > 465

o

c.

a=6·568 (6), c=8-411 (8) A. We wish to thank Ir. F.X.N.M. Kools and Ir. W. G.

Hol for their earlier work pertinent to this research.

d f/f 1 hkl 5·693

A

15 100 4·718 60 101 4·205 20 002 3·383 80 102 3·287 100 110 3·062 3 111 2·846 5 200 2·826 5 201 2·589 15 112 2·516 10- 103 2·357 30 202 2·149 3 210 2·103 5 004 2·084 5 21.1 1·9965 3 203 1·9147 15 212 1·8968 15 300 1·7713 10 114 1·7286 5 302 1·7061 5 213 1·6421 5 220 1·5508 3 311 1·5288 3 222 L120 -0·01 - 0·03 -0·01 - 0·01 - 0·03 - 0·03 -0·02 - 0·02 - 0·01 - 0·01 - 0·01 +0·02 0·00 - 0·03 +0·01 - 0·01 - 0·02 - 0·01 0·00 +0·01 - 0·01 -0·01 +0·04

One of us (AvdA) thanks the Netherlands Organi -zation for the Advancement of Pure Scientific Research (Z.W.O.) for financial support.

References

CAILLET, P. (1967). Bull. Soc. chim. Fr., 4750.

GATEHOUSE, B. M. & LEVERETT, P. (1969). J. Chem. Soc. A, p. 849.

HOERMANN, F. (1929). Z. anorg. Chem. 177, 145. KLOOSTER H. S. VAN (1914). Z. anorg. al!g. Chem. 85, 49. KOOLS, F. X. N. M., KOSTER, A.

s

. &

RIECK, G. D. (1970).

Acta Cryst. In the press.

KosTER, A. S., KooLs, F. X. N. M. & RIECK, G. D. (1969).

Acta Cryst. B25, 849.

LIEMPT, J. A. VAN (1922). Z. anorg. Chem. 122, 175. SALMON, R. & CAILLET, P. (1969). Bull. Soc. chim. Fr.,

1569.

SCHMITZ-DUMONT, 0. & WEEG, A. (1951). Z. anorg. a!lg.

Chem. 265, 139.

SPITZYN, V.I. (1947). J. Gen. Chem. USSR, 17, 11.

J. Appl. Cryst. (1970). 3, 392

Three-Dimensional Graphical Models of

Molecules and a Time-Slicing Computer

BY EDGAR MEYER

Department of Biochemistry & Biophysics, Texas A&M University, College Station, Texas 77843,U.S.A. and

Department of Chemistry,* Brookhaven National Laboratory, Upton, L. !., New York 11973, U.S.A.

(Received 12 November 1968 and in revised form 19 January 1970)

A series of computer programs has been written to prepare and display graphical models of molecules

in three dimensions. A time-slicing computer is used to allow the operator to interact freely with the display through various options built into program DISPLAY. Two stereo views are drawn in separate

colors on a color television monjtor and viewed through filters for the three-dimensional effect. These techniques may prove useful both for information retrieval and for assistance with the crystallographic determination of molecular structures.

Introduction

Graphical display of the output from a digital com-puter is still a relatively novel technique in crysta l-lography. Several significant display techniques are currently in use.

*

Research Collaborator, 1968-1970,

The program ORTEP (Johnson, 1965) takes atomic coordinates and prepares two stereo images on the output device, usually an X-Y plotter. Such stereo images are finding increasing use as three-dimensional illustrations in scientific books and journals.

A second approach (Levin thai, 1965; Levinthal,