The superstructure ofstannoidite

Zeitschrift fur Kristallographie, Bd. 144, S. 145-160 (1976)

The superstructure of stannoidite

By YASUIIUW KrDoH and Y. TAKEUCHI

Mineralogical Institute, Faculty of Science, University of Tokyo, Rongo, Tokyo

(Received 1 April 1976)

Auszug

Die Kristallstruktur von Stannoidit CUle(Fe, Zn)eSn4S24 wurde mittelspartieller Pattersonsynthesen bestimmt und bis R = 0,064 verfeinert. Fureinen Kristall von del' Konjo Mine in Japan sind die Gitterkonstanten:

a= 10,767(1) A, b = 5,411(1) A, c = 16,118(2) A, Z = 1; Raumgruppe ist

1222. Die Struktur liif.Jt sich von del' Struktur von Zinnkies, CU2(Fe, Zn)SnS4,ableiten, wenn darin ein Teil des Sn durch Cu ersetzt und auf.Jerdem ein Uber-schuE von Cu in den tetraedrischen Lucken untergebraeht wird. Die vonS.Atomen gebildeten Tetraeder urn die iiberschiissigen Cu-Atome haben mitbenachbarten Tetraedern gemeinsame Kanten. Del' kiirzeste Abstand zwischenzwei Metallatomen betriigt 2,70 A. Die Metallatome scheinen im wesentlichengeordnet zu sein. Von drei voneinander unabhiingigen S-Atomen sind zwei wiebeim Zinnkies an ,,"wei Cu-Atome und je ein Fe(Zn)- und Sn-Atom gebunden;das dritte hat vier Cu-Atome und ein Fe-Atom zu Nachbarn.

Abstract

The crystal structure of stannoidite, CUle(Fe,Zn)eSn4S24, a derivative ofstannite, CU4(Fe, ZnhSn2Ss, has been determined from consideration of thepartial-Patterson syntheses and refined to R = 6.40/0, using a crystal fromKonjo mine, Japan: Space group is 1222, a = 10.767(1) A, b = 5.411(1) A,

c = 16.118(2) A, Z = 1. The results revealed that the structure of stannoiditeis derivable from the stannite structure by substituting Cu atoms for a set of Snatoms in stannite and adding excess Cu atoms in a set of tetrahedral vacancies.The tetrahedra formed by sulfur atoms about the excess Cu atoms share edgeswith neighbouring tetrahedra, the shortest metal-metal distance being 2.70 A.Metal atoms in the structure seem to be essentially ordered. Of three independentsulfur atoms, two are bonded, like those of stannite, to two Cu, one Fe(Zn),and one Sn, while the third sulfur atom is bonded to five metal atoms: fourCu and one Fe.

Introduction

Stannoidite (SPRINGER, 1968; PETRUCK, 1973; YAMANAKA and

KATO, 1976), Cus(Fe,ZnhSn2S12, which was established by KATO(1969) as a new mineral speCles, IS a derivative of sphalerite, the cell

Z. Kristallogr. Bd. 144, 3/4 10

146 YASUHIRO KUDOH and Y. TAKEUCHI

volume of which is six times that of the basic structure. Based uponM:ossbauer spectra, YAMANAKAand KATO (1976) proposed the followingpartitioning of valencies: Cu~+Fe~+(Fe2+,Zn2+)Sn~+Si2' The crystalstructure of this metal-excess derivative of the sphalerite structure hasnow been worked out with the results as reported in the present paper.

Experimental

Unit cell and space group

Crystals used for the present study came from the type locality,Konjo mine, Japan. As shown in Table 1, the chemical compositionof the crystals may well be expressed by CU15.94(Fe4.5oZnl.So)Sn4.04S24.

The following cell dimensions were determined with least-squaresrefinement based on reflections measured on a four-circle automaticdiffractometer: a = 10.767(1) A, b = 5.411(1) A, c = 16.118(2) A. Forthis refinement, a program was used written by ApPLEMAN (EVANSet al., 1963).

The unit cell contains one formula unit, the calculated densitybeing 4.655 g . cm-3. In Table 2, the cell dimensions are comparedwith those of related minerals.

X-ray photographs revealed, as reported by KATO (1969), a markedsubstructure; the axes of the sub cell a', b' and c' are related to thoseofthe original cell as follows: a' = aj2, b' = b, c' = cj3. The extinctionrule is consistent with those of the space groups 1mmm, 1mm2, 1222and 1212121. Of these, only the last two are consistent with the tetra-hedral framework characteristic of the sphalerite structure. Since thepossible space group of the substructures was found to be A222, weassumed, for structure analysis, the space group 1222. In this space

Table 1. Chemical composition of stannoidite*

Numbor of atoms, based on 12 sulfur atoms

CuFeZnSnS

39.189.734.56

18.5629.77

7.972.25

}3.15

0.902.02

12.00

Total 101.80

* SPRINGER (1972, private oommunication).

Cell dimcnsions SpaceMineral

aI

b c group

stanni te 1

AICU4(Fe, Zn)2 Sn2Ss 5.448 (= a) 5.371 (X 2)A 142m

stannoiditcCU16(Zn,Fe )2Fc4Sn4S24 5.384 ( X 2) 5.411 A 5.373 (X 3) 1222

mawsoni te 2

CU24 FegSn4S32 5.373 (x 2) (= a) 5.355 (X 2)*

The superstructure of stannoidite 147

Table 2. Cell dimensions and symmetries of stannoidite and related minerals

* Probable spacc group2: 142m, 14mm, 1422 or 14122.1 HALL and STEWART (1974, private communication).2 YAMANAKA and KATO (1976).

group, which was confirmed through structure analysis, a set of two-

fold axes have, like that in A 222, a point in common.

Intensity measurement

The dimensions of the crystal used for intensity measurementswere approximately 0.12 X 0.16 X 0.28 mm3. The 2e-w scan tech-nique was used to measure intensities on a four-circle diffractometer.The number of reflections out to 2e = 650 for MoK exwas 429. After

correcting for Lorentz and polarization factors, the intensities werereduced to structure factors. Corrections for absorption (fl = 159.27cm-1) were made using the program ACACA written by PREWITT(WUENSHand PREWITT, 1965).

Determination and refinement of the structure

The unit cell of stannoidite, whose volume is six times that ofsphalerite, contains 24 sulfur atoms and a total of 26 metal atoms,specifically 16 Cu, 6 (Fe, Zn) and 4 Sn. It was thought that this deriva-tive structure is, in principle, characterized by locations of two excessmetal atoms and four heavy atoms, Sn. These atoms were readilylocated in the vector space based on the following consideration.

Let E be the set of excess atoms and B the set of remaining atoms,the arrangement of which is based on the sphalerite (blende) structure.Then the vector set of the entire structure may be separated into twoparts:

v = V(B)+ V(EB);

10*

148 YASUHlRO KUDOH and Y. TAKEUCHI

oo@

0,0I

, I ,',

'~'"/'/:<

- - - -:i~;~\~~4c:r

- - - -")@j)

al2

cl2

o

Fig. 1. Portion of the partial,Patterson section, y = 0, showing the location ofSn, indicated by P. Contours at equal, but arbitrary, intervals; negative con.

tours dotted. Broken lines indicate the sphalerite superlattice

the first term represents the vector set of B, and the second that ofE plus the set of cross vectors between E and B. Since the atoms inE are presumably located in interstices of a tetrahedral frameworkof B of the sphalerite type, none of the non origin vectors of V(EB)should coinside with those of B. If the two excess atoms of E areordered at a specific set of interstices, the positions should be, ac-cording to the space-group requirement, on a set of twofold axeswhich are separated from each other by translation (a + b + c)(2.This situation secures, in V, a direct observation of the image of Basseen from E.

In practice, we calculated the partial-Patterson function (TAKEU-CHI, 1972) based on hkl reflections other than h = 2n and l = 3n,(n an integer). In this particular case, the peak due to vectors betweenthe excess atoms and Sn should appear in the function as a positivepeak having the highest density. In this way, the location of Sn was

Table 3. Point symmetries at metal sites, average M-S lengths and temperaturefactors of metal atoms

Sito notation M(l) M(2) M(3) M(4) M(5) M(6) M(7)

Point symmetry 222 222 222 2 2 2 1Multiplicity 2 2 2 4 4 4 8Possible site content [4Cu, 2(Zn, Fell)] (4FeIlI,4Cu) Sn Cu

<M-S> 2.35 2.26 2.30 2.3:~ 2.34 2.40 2.32 .AB 1.1 1.6 1.6 1.3 0.9 0.4 1.5 .A2


directly determined in the y = 0 section of the function (Fig. 1). Forthe present purpose, the locations of the excess atoms and Sn provideenough knowledge to determine initial phase angles of the super-structure reflections. The initial set of atomic coordinates were thenderived by substituting Cu for Zn in the tetrahedral framework ofsphalerite and by distributing Sn and the excess atoms according tothe above results; all metal atoms other than Sn were tentativelyrepresented by Cu. Structure-factor calculations based on the atomiccoordinates gave R = 0.168 for all observed reflections. Full-matrixleast-squares refinement with isotropic temperature factors was thencarried out using the program ORFLS (BUSING, MARTIN and LEVY,1962), and applying an equal-weighting scheme. Several cycles ofcalculations reduced the R value to 0.085.

At this stage, an attempt was made to differentiate between theatomic species Cu and Fe(Zn); they might be distributing in anordered fashion as those in the low-temperature form of chalcopyrite(HALL and STEWAR'1', 1973) and related sulfides. According to thestudy on Mossbauer spectra and chemical composition (YAMANAKAand KATO, 1976), the iron atoms in stannoidite are mostly in the stateof FeIII; Fell substitutes for Zn, yielding a cell content which maywell be expressed by CU16(Zn,Fe hFe4Sn4S24. Based on multiplicities ofmetal sites, the problem is then reduced to that of distributing Fe andCu in the M(l), M(2),...M(5) sites (Table 3); the eightfold site M(7)should be for Cu, provided that significant disorder is substantiallyabsent. Note that the location of Sn, as determined by the structureanalysis, is denoted in Table 3 as M(6). As shown by FRUEH (1953) forchalcopyrite, a Patterson synthesis based on the superstructure reflec-tions only was expected to be helpful to the present purpose. In thiscase, however, it did not work well because of the presence of heavyatom, Sn, and the distortions of peaks due to atomic displacements.


e/2

0/2 o

Fig. 1. Portion of the partial-Patterson section, y = 0, showing the location ofSn, indicated by P. Contours at equal, but arbitrary, intervals; negative con-

tours dotted. Broken lines indicate the sphalerite superlattice

the first term represents the vector set of B, and the second that ofE plus the set of cross vectors between E and B. Since the atoms inE are presumably located in interstices of a tetrahedral frameworkof B of the sphalerite type, none of the nonorigin vectors of V(EB)should coinside with those of B. If the two excess atoms of E areordered at a specific set of interstices, the positions should be, ac-cording to the space-group requirement, on a set of twofold axeswhich are separated from each other by translation (a + b + c)j2.

This situation secures, in V, a direct observation of the image of B asseen from E.

In practice, we calculated the partial-Patterson function (TAKEU-CHI, 1972) based on hkl reflections other than h = 2n and l = 3n,(n an integer). In this particular case, the peak due to vectors betweenthe excess atoms and Sn should appear in the function as a positivepeak having the highest density. In this way, the location of Sn was

Table 3. Point symmetries at metal sites, average M -8 lengths and temperaturefactors of metal atoms

Site notation M(l) M(2) M(3) M(4) M(5) M(6) M(7)

Point symmetry 222 222 222 2 2 2 1Multiplicity 2 2 2 4 4 4 8Possible site content [4 Cu, 2(Zn, Fell)] (4FeIII, 4Cu) Sn Cu

<M-S> 2.35 2.26 2.30 2.33 2.34 2.40 2.32 AB 1.1 I.G 1.6 1.3 0.9 0.4 1.5 ;\2


directly determined in the y = 0 section of the function (Fig. 1). Forthe present purpose, the locations of the excess atoms and Sn provideenough knowledge to determine initial phase angles of the super-structure reflections. The initial set of atomic coordinates were thenderived by substituting Cu for Zn in the tetrahedral framework ofsphalerite and by distributing Sn and the excess atoms according tothe above results; all metal atoms other than Sn were tentativelyrepresented by Cu. Structure-factor calculations based on the atomiccoordinates gave R = 0.168 for all observed reflections. Full-matrixleast-squares refinement with isotropic temperature factors was thencarried out using the program ORFLS (BUSING, MARTIN and LEVY,1962), and applying an equal-weighting scheme. Several cycles ofcalculations reduced the R value to 0.085.

At this stage, an attempt was made to differentiate between theatomic species Cu and Fe(Zn); they might be distributing in anordered fashion as those in the low-temperature form of chalcopyrite(HALL and STEWART, 1973) and related sulfides. According to thestudy on Mossbauer spectra and chemical composition (YAMANAKAand KATO, 1976), the iron atoms in stannoidite are mostly in the stateof FeIII; :Fell substitutes for Zn, yielding a' cell content which maywell be expressed by CU16(Zn,:Fe)2Fe4Sn4S24.Based on multiplicities ofmetal sites, the problem is then reduced to that of distributing Fe andCu in the M(1), M(2),...M(5) sites (Table 3); the eightfold site M(7)should be for Cu, provided that significant disorder is substantiallyabsent. Note that the location of Sn, as determined by the structureanalysis, is denoted in Table 3 as M(6). As shown by FRUEH (1953) forchalcopyrite, a Patterson synthesis based on the superstructure reflec-tions only was expected to be helpful to the present purpose. In thiscase, however, it did not work welI because of the presence of heavyatom, Sn, and the distortions of peaks due to atomic displacements.

Site AtomI

xI

yI

z

M(l) Zn(FeII) 0 0I

0M(2) Cu 1 0 02

I

M(3)* Cu 0 0 12

M(4) Cu 0.2511(4) 0 1I 2

M(5) FeIlI 0 0

I

0.3298(3)M(6) 8n 0 l 0.1693(1 )2M(7) Cu 0.2465( 3) 0.0107(11) I 0.1695(2)8(1) 8 0.1308(13) 0.2443(12) I 0.0826(5)8(2) 8 0.3792(10) 0.7558(13)

I

0.0801(5)8(3) 8 0.1294(14) 0.7488(12) 0.2546( 5)

Site fJH fJ22 fJI2 fJI3 fh3 B,

0.013(2)10.0006(2)1I

1.13A2M(l) 0.0030(4):M(2) 47(5)1 14(2) 13(2) 1.64M(3)* 34(8) 19(3) 11(3) 1.57M(4) 31(3); 12(1) 10(1) I 0.0007(12) 1.29M(5) 27(3); 8(1)1 6(1) -0.001 ( 3) 0.86M(6) 14(2) 2(1) 4(1) 0.0001 (15) 0.44M(7) 39(2), 12(

'Ii

15(1) - 7(10) -0.0002(1) 8( 8) 1.52S(l) 28(5)! 7(2) 8(2) -21( 9) 2(3) -14( 4) 0.888(2) 24(5)1 9(2) 7(2) 27( 7) 1(2) -15( 4) 0.81

8(3) 21(5) 6(2) 8(1) -31( 7) 3(2) - 2( 4) 0.66


In dealing with metal ordering in similar structures, HALL andROWLAND(1973) and HALL and STEWART(1973) suggested that thermalparameters may be useful; the temperature factors of the Cu atomstend to be significantly higher than those of Fe (SZYMANSKI,1974;ROWLAND and HALL, 1975). As observed in Table 3, M(7) in whichwe located Cu, indeed has a high B value. We find that M(2), M(3) andM(4) likewise have high B values, suggesting Cu atoms for these sites.M(1) and M(5) are then the sites of Fe(Zn); specifically Zn(Fe) inM(1) and FeIII in M(5). This mode of metal ordering is found to besatisfactory on the compositional ground. In this case, as will be dis-cussed later, the four-coordinated S atoms are bonded to two Cu, one

Table 4. Final atomic parameters and standard deviations (in parentheses)

The anisotropic temperature factors are expressed in the form exp {-(h2/31l

+ k2fJ22 + l2/Ja3 + 2hkfJI2 + 2hlfJI3 + 2kl/h3)}.The B;s are equivalent isotropic values (HAMILTON, 1959).

* Interstitial atom.


Table 5. Comparison of observed and calculated structure factors for stan ~oidite

F F F F F F F F F F F F

." lul 7HI, 7Hi' '06 371

"8, 86 16 '01 17

393 '89 HZ ~:; 121 29H 1)0'"

6) 6..613 616 50 60 ')2(, ')U\ '219 227 76

"16

" '"137'"

116 118'9 53 4') )2

21,0 :!!J4 122 127 73 76108 112

"72 57 56

"42 1,2 17 67 60

116 108 ')2 89 102 94 68 6','"

5185 79 60 6'. 65 62 ',8 ',1

°12 1t15 ,o6

'055

81 71, 77 72 1')0 11.666

"'00 It82 1.2 38 J1J 301, 1 17 87 .-!,12

17' '.1 '51,2

"

, 74 72

5' "'267 27') 42 1,7

"'9

52 59 61178 175 7') 79 71

"%05 38' 234 226 79 75 '.8 1,1' 17 ',6 6223' 226 6, 76 510 485

" "36. 359 78 76'"

11,1 58 50 12 110 102 1 17 58 5650 60 272 2117 265 21,<) , 62 ,6

117 106 57 55 2:')7 2-,H78 71 86 H5 232 216

"0 1°

"17 7lJ 71

87 A7 96 ')5 60 ';3 170 171."

6661

"<)2 H7 80 75

"'.)

"52

69 72 ",2 ',6J,)

'"" '"

60 57 )4 ')2 11 '.:.! ',1 17 '.2"12 36} ;28

610 590 10'3' 292 121 116 11 65 60 11

"1) 17 54 52

234 224 261 261 268 252 ')1, 51,'.2 ..7

"91,D8 201 ")0 70 5q

96 97

" " " "168 152 17 55 57

11 62 }4 Iii 67

"69 62

"50

10

"55 '9 '7

15

"39 60 61

"85 50

"

8) 67 1,1,

"II 18 117 155

"'9 '., 16 , 10 67 72 2 16, }63

6'68 I) 75 (is

", S2"

6i 66 ,99 108

61 6, 10 (,2 62 52 58

" '"11,0 63

5'1.2 22 1.5

" "'.8 18 68

"]119 )29

" "67 67

106 .)6

"181 18) 61 )2 0

"68 ')7

"65

168 154 6) 57 57 62 , ";2 50

"72 72 60 61

°18 350 358

" '0 '5 55 '8 5'. '., ') 16 1"

54 se 2 120 12769

" " ",

"1.5 , 286 273

"85 0 10 6, 7}

'5"15

"3<}'"

(,5 69 1~

"V.

"J')

"5'. 59v,

"P. 6, 61 6, 69

16 229 20) 56 '.0 10 Jib 51 61 52 ("

"91

"52 )6 45

"56 I,h

6(, 75 56

"" °18 115 107

81 76 87 80 5:1 60

"",

"267 26,

55 61 7} 6')'" "93 71 5') >7 57 ')6

" '" "'.2 '., 0 18 65 6)

6, 54"

J7"

50" '"75 70 1.'1

"9' 77 70 70'9 1'15

"p. ';2

"0 20 "i9 656,

'"67 68 1.5 J6 '. '.,

"61 58 55 611 62 ';5"

'., 17

"'.1 ..2 '.7 1 20 52

""53 51

"-;3 36 0 15 fil. 70 ..6

"" " " '.7 27 75 77'5 "

36 60 61 ';5 ,6 1 20 50 526J 55 6, 62

"65 :)1. 57

60 55 109

" " "77 68 51

"69 51, 51 ';4 1 1'; JJ9 31110

"J7 6, 65 79 71, , :!72 277 1 211

" "72 .7 111; 97 5 211 201 , '.) 5112

"'5

121 101

"1,1. ."

"" '" 9' 78 62 62 0 15 72 75 1 20

"'9

"57

")0

". "2

"55 ,

" "93 92 70 6,0,77 75 87 (,8

"50 11 80 6(, 50

"o 20

"52

52"

.- 70"

39 57 53

"52 50 50 66

"0 15

"7'. 0 21 55 57

99 97 2 66 66 2" "" "

92 77 61 60 92 82 , 65 61 , '., 51

"51 76 65 56

"7'j 68

'9"

'.R"

55 57 15 262 26q 1 21 181 20770 71 233 225 , 175 17)

'9"

503'

I)'.7 J3 58 55

'"'79..5 28 62 55 0 21

" "89"

15 51"

2'5

56 r.o 53 5370 6) 71 60 6,

", '.,

"60"

51"

108"5 57 55 2 21

"50

"5' 91

9' 15 56 61

"51 87 85 I:.! ,6

"~,A 57 1 21 171 168

61 ';5

"57 52

5'11 61 60 51" " " "

o 21 1.2'960 59 506 '93 1 I, 1')5 11'15

"3'

12'5

'"626 381 12 616 618 , 1hO 16') 2 22

"55

274 21'10 240 2341J 52 J7 ,o6 )<)4 1~2 171'1 1,41 425 11 0

"56

'.'o 22 60 5681, 797 106 101.

133 11,2 219 230 76

"0 16 6'. 77 1 23 1.2 52

121 127 375 )62 ,0 93°

12

" ", '.,

"85 91 59 fi5 2"' "

1 23 59 66

"71

"'108 ')8 63 71 70 1 Hi '.,

"56 51 ,6"

61 66 1 2)

"5'OJ 8', 1.2 1,2 1 16 55

"692 658 72 66°

12 233 234

"'.1

()24

'"501 '96 95 95 , 523 502330 317 4')

"76 7} ,

"7 "7 2 16 52 61 0

" "';HlB') 214

"'.1. 6J ('3 6 286 271,


Zn(Fe),and one Sn. This is essentially the same coordination as thatin stannite; the proposed model therefore appears to be acceptable.Assuming various ordering in models other than this, we carried outcycles of refinements, but we did not obtain any results which rule outthis ordering model.

Based on this model, therefore, we carried out least-squares re-finement with anisotropic temperature factors which converged togive R = 0.064; the weighting used was of the form (CRUICKSHANKet al., 1961):

w = lj(a + Fo + CFo2), a = 2Fmin = 10.0, C = 2jFmax = 0.004.

Finally, corrections for anomalous dispersion were applied using Ill',

111" values given by CROMER (1(65). Excluding hkO, Okl and holreflections, least-squares refinements were carried out for the workingmodel of structure and its centric equivalent, giving R = 0.066 and0.064 respectively. According to the significance test (HAMILTON,1(65), the difference in R was found to be significant. The atomiccoordinates given in Table 4 are those obtained by the refinement ofthe latter model. Observed and calculated structure amplitudes arecompared in Table 5.

Discussion

Compared to stannite (Table 2), stannoidite is deficient in Sn buthas an excess of Cu; it has in total of two excess metal atoms. Thestannoidite structure that bears a superstructure relation to stanniteis, in principle, characterized by the distribution of Sn in its structure(Fig.2). The relationship may best be eXplained in the following way.In the body-centered lattice of stannite, with Sn at each lattice point(Fig. 3), if the sublattice defined by translation vectors t and t' issuppressed, the remaining array of 8n atoms define another sub latticethat corresponds to the stannoidite lattice. The structure of stannoiditeis then derived by locating Cu atoms in the set of tetrahedral positionsfrom which Sn atoms were removed, and by filling the tetrahedralvacancies adjacent to the tetrahedra of new Cu atoms with excessmetal atoms (Fig. 4). In the result, the stannoidite structure has aswhole a remarkable similarity to the stannite structure.

Of three independent sulfur atoms, S(1) and 8(3), which areunaffected by the presence of interstitial atoms, have essentially thesame coordination as that in stannite; each of these are bonded totwo Cu, one Zn(Fe) and one Sn (Fig. 5). Bond lengths in these COOf-


(a)

o Cu

(b)

@Zn Os@Fe 8Sn

Fig. 2. Comparison of the crystal structures of (a) stannite, CU4(Fe,Zn)2Sn2SS,and (b) stannoidite, CU16(Fe,Zn)6Sn4S24

,,- -q- - - - - - - - - -0,- - - - - -- - - ~Q---

\ , \, \---;-

\

I

o\ ,

,\ , o

, , , , ,o

o, , , , , o

,\ 0, ,,

"~" \ \

- - (J- - - - -- - - - -0- - - - - . - - - - Q- - -\ \ \, \ ,

o '~t'

, , , , , oo

o,\

\\ o

,,\ 0

Fig.3. The body-centered lattice of stannite (ST), showing, by circles, locationsof Sn at lattice points (heavy and light cireles are respectively at y = 0 andy

= !). If the sublattice indicated by broken lines is removed, the remainingset of lattice points defines another sub lattice corresponding to that of stan-

noidite (STD)

~@ tv yz1/2

0 @ @ <g Y;:;:0,1

Cu (Zn,FJI) FJI Sn

fj Y;:;:lit,~u

0 Yz31t,

S


a M(2)M(3')

(a)

o(b)

Fig. 4. Comparison of tho structures of stannoidite and stannite: (a) The b.axisprojeotion of the stannoidite structure. (b) The stannite struoture (HALL and

STEWART, 1974, private oommunioation), as viewed along the b axis

(a)

Fig. 5. Coordinations of S(l) and 8(3)

(b)

dination about the sulfur atoms agree closely with the correspondinglengths of stannite (Fig. 6). The result may in turn suggest that theproposed ordering model may well be correct. Although some disorderwould probably be expected for this sort of structures, it would not bea predominant feature for stannoidite.

ivM(l) ivM(2) ivM(3) ivM(4) iVM(5)I

iVM(6) ivM(7) Ls

iVS(l) 2.35A 2.30A 2.421\ 2.26A 2.33A(1,4) (1,2) (1,2) (1,1)

VS(2) 2.26A 2.30A 2.36 2.39A 2.45 2.35(1,4) (1,4) (1,2) (1,2) I (1,1)

iVS(3) 2.29

I

2.38 2.34 2.31(1,2) (1,2) (1,1)

I2.22

I

(1,1)

LM 2.35 2.26 2.30 I 2.33 2.34 2.40 2.32,

155The superstructure of stannoidite

(a)

CFe.Zn)

(b)

Fig. 6. Comparison of neighbours of S(2) in stannoidite, (a), and those of Sinstannite, (b), (HALL and STEWART, 1974, private communication)

Bond lengths and angles in the stannoidite structure are given inTable 6a, b, in which we find that the M(2)-8(2) lengths have anunusually small value, 2.26 A; in tetrahedral structures, Cu-8 lengthsare, without exception, around 2.31 A (TAKEUCHI and OZAWA, 1975).

Sulfur atom 8(2) is bonded, unlike 8(1) and 8(3), to five metal atomswhich include the interstitial atom M(3). This short bond length isthen thought to be related to possible distortions of coordination poly-hedra caused by the presence of Cu in M(3).

Table 6a. Interatomic di8tance8

Estimated errors for each bond length are::!:: 0.01 A. Numbers in parenthesesindicate the number of bonds reaching the sulfur (left) and the number of bondsreaching the metal (right). The Roman numeral denotes the coordinationnumber. Ls and LM represent the average distances around sulfur and metal,respectively.


Table 6b. Edge lengths oj polyhedra and bond angles

I !Edge length

I

AngleCoordination group

I

N eighbours

I

(IJ = 0.02 A) (IJ = 0.5')

Tetrahedron about M(1) S(l) S (1 )ap 2.75A(x 2) 106.2°(x 2)S(1 )p 3.86 (x 2) 110.8 (X 2)

S (1)ap S(1)p 3.88 (X 2) 111.4 (X 2)average 3.50

I

M(2) S(2)w S(2)s :3.71 (X 2) I11 O.3 (X 2)

S(2)q 3.69 (X 2) 109.7 (X 2)S(2), S(2)q 3.66 (X 2) 108.4 (X 2)average 3.69

M(3) S(2) S(2)8 3.80 (X 2) [111.6 (X 2)S(2)q 3.79 (X 2) 1111.0 (x 2)

S(2)s S(2)q 3.66 (X 2) 105.8 (X 2)average 3.75

M(4) S( 1)8 S(1)r :3.84 113.0S(2)8 3.85 (X 2) 111.4 (X 2)S(2)s 3.75 (X 2) 107.0 (x 2)

S(2)s S(2)r 3.79 106.9average 3.81

M(5) S(2hp S(2h 3.80 105.2S(3)w 3.83 (X 2) 109.5 (X 2)S(3)wp 3.79 (X 2) 108.0 (X 2)

S(3)w S(3)wp 3.89 116.1average 3.82

M(6) S(1) S(1)wp 3.95 109.4S(3) 3.89(x)2 108.5 (X 2)S(3)wp 3.94(X)2 110.6 (X 2)

S(3) S(3)wr> 3.87 109.3average 3.91

M(7) S(1) S(2)w 3.76 105.7S(3)w 3.86 113.9S(3hp 3.68 110.4

S(2)w S(3)w 3.89 108.5S(3hp 3.77 107.4

S(3)w S(3hp 3.75 110.6average 3.79


Table 6b. (Continued)

Coordination group Neighbours

I

Edge length

I

Angle(a = 0.005 A) (a = 0.5°)

Tetrahedron about 8(1) M(l) M(4)u 3.808 A 110.0 °M(6) 3.843 107.5M(7) 3.810 111.6

M(4)u M(6) 3.825 108.2M(7) 3.805 113.0

M(6) M(7) 3.749 106.4average 3.807

Trigonal",pymmid abont 8(2)

I

M(2)v M(3)ur 2.705 72.9M(4)u 3.825 111.9M(5)us 3.853 111.9M(7)v 3.863 110.0

M(3)ur M(4)u 2.703 71.0M(5)us 2.743 71.6M(7)v 4.749 177.1

M(4)u M(5)us 3.851 108.4M(7)v 3.886 107.8

M(5)us M(7)v 3.884 106.5average 3.606

Tetrahedron about 8(3) M(5)v M(6) 3.743 106.6M(7)u 3.802 114.5M(7)v 3.704 106.1

M(6) M(7)u :~.7H8 110.0M(7)v 3.832 108.7

M(7)u M(7)v 3.748 110.4average 3.766

[0] to [w] are code indicators showing coordinates of atoms equivalent by spacegroup operation to the atoms at xyz. Corresponding operations are:

[0] twofold rotation at 0, y, 0[p] twofold rotation at 0, 0, z[q] twofold rotation at x, ~, 0

[r] twofold rotation at !, y, 0[s] twofold rotation at ~, }, z

Two code indicators in sequence imply an atom related to the one at xyzby successive application of the two symbolized operations.

[t] twofold screw at x, t, t[u] twofold screw at t, y, t[v] translation b[w] translation -b.

The location of each tetrahedral interstice in which M(3) occurs is

such that it is surrounded by six metal atoms, M(2) [X 2], M( 4) [X 2]

and M(5) [X 2], each having tetrahedral coordination (Fig.4). An


Tb

1

I- -B

Fig. 7. Showing that by sharing edges, tetrahedra M(2)-S and M(3)-S form aninfinite ehain parallel to the b axis. The subscripts, n, r, refer to Table 6

opposite pair of edges of the M(3) tetrahedron are shared by M(2)tetrahedra to form an infinite chain parallel to the b axis (Fig. 7). Theremaining four edges of M(3) tetrahedron are shared with M(4) andM(5) tetrahedra; the metal atoms, M(5), M(4) and M(3) are in a planeperpendicular to the chain axis. The atoms, M(4) and M(5), are dis-placed from the ideal metal positions of the respective pseudocubicsub cell, giving rise to lengthenings of the M(4)-S(2) and M(5)-S(2)distances. As shown in Fig. 6, the M(7)-S(2) distance is even longer;presumably M(7) is more strongly bonded to S(1) and S(3) as seen inTable 6a. It follows that bonding to S(2) depends, to a great extent,on M(3) and M(2); the M(2)-S(2) and M(3)-S(2) bonds tend to beshort.

The M(2) corresponds to the Sn position in the stannite structurefrom which the Sn atom was removed, as mentioned earlier, to derivethe stannoidite structure. Therefore, suppose that M(2) in Fig.6 is

The superstructure of stannoidito 159

replacedby Sn and M(3), the extra atom is removed; we then find thatthe resulting coordination about S(2) is essentially the same to thatofthe corresponding sulfur atom in stannite. This would mean that theeffecton bonding caused by removing Snlv from the stannite to derivestannoidite is supplemented by adding two CUI atoms. The structureof mawsonite (Table 2), the other mineral which is closely related tostannite, would probably be based on the same principle.

Acknowledgements

The authors express their thanks to Dr. S. R. HALL, Departmentof Energy, Mines and Resources, Ottawa, Canada, who kindly per-mitted us to quote his results of the refinement of the crystal structureof stannite in advance of publication and gave us valuable comments,and to Dr. A. KATO, National Science Museum, Tokyo, for furnishingspecimens and valuable discussion. Thanks are also due to Dr.T. YAMANAKAof our Institute for useful discussions and suggestions,and to Professor Y. IITAKA, Department of Pharmaceutical Science,University of Tokyo, for making his automatic diffractometer availablefor the present investigation. Computations were carried out onHITAC 8700/8800 at the Computer Center of the University of Tokyo.

References

W.R. BUSING, K. O. MARTIN and H. LEVY (1962), ORFLS, a FORTRAN crys-tallographic least-square program, ORNL-TM-305, Oak Hidgo NationalLaboratory, Tennessee.

D. T. CROMER (1965), Anomalous disporsion corrections computed from self-consistent field relativistic Dirac-Slater wave functions. Acta Crystallogr.18, 17 - 23.

D. W. J. CRUICKSHANK, DIANA E. PILLING, A. BUJOSA, F. M. LOVELL andMARY R. TRUTER (1961), Crystallographic calculations on the ForrantiPegasus and Mark I Computers. In: HAY PEPINSKY, J. M. ROBERTSON andJ. C. SPEAKMAN, Ed., Oomputing methods and the phase problem in x-raycrystal analysis. Pergamon Press, Oxford, p. 32.

H. T. EVANS JR., D. E. ApPLEMAN and D. S. HANDWERKER (1963), ArneI'.Crystallogr. Assoc. Meeting, Cambridge, Program and Abstract, 42.

A. J. FRUEH (1953), An extonsion of the "difforence Patterson" to facilitate thesolution of order-disorder problems. Acta Crystallogr. 6, 454-456.

S. R. HALL and J. F. HOWLAND (1973), The crystal structure of syntheticmooihoekite, CU9Fe9S16. Acta Crystallogr. B 29,2365-2372.

S. R. HALL and J. M. STEWART (1973), The crystal structure refinement ofchalcopyrite, CuFeS2. Acta Crystallogr. B 29,579-585.

W. C. HAMILTON (1959), On the isotropic temperaturo factor equivalent toa given anisotropic temperature factor. Acta Crystallogr. 12, 609- 610.


W. C. HAMILTON (1965), Significance tests on the crystallographic R factor.Acta Crystallogr. 18, 502-510.

A. RATO (1969), Stannoidite, CU5(Fe,ZnhSnSs, a new stannite-like mineralfrom the Konjo Mine, Okayama Prefecture, Japan. Bull. Nat. Sci. Mus.Tokyo 12, 165-172.

W. PETRUCK (1973), Tin sulphides from the deposit of Frunswick Tin MinesLimited. Can. Mineral. 12, 46-54.

J. F. ROWLAND and S. R. HALL (1975), Haycockite, CU4Fe5Ss: a superstructurein the chalcopyrite series. Acta Crystallogr. B 31, 2105-2112.

G. SPRINGER (1968), Electroprobe analyses of stannite and related tin minerals.Mineral. Mag. 36, 1045-1051.

J. T. SZYMANSKI (1974), A refinement of the structure of cubanite, CuFe2Sa.Z. Kristallogr. 140, 218~239.

Y. TAKEUCHI (1972), The investigation of superstructures by means of partialPatterson functions. Z. Kristallogr. 135, 120-136.

Y. TAKEUCHI and T. OZAWA (1975), The structure of CU4Bi4Sg and its relationto the structures of covellite, CuS and bismuthinite, Bi2S3. Z. Kristallogr.141,217-232.

B. J. .WUENSCH and C. T. PREWITT (1965), Corrections for x-ray absorption bya crystal of arbitrary shape. Z. Kristallogr. 122, 24-59.

T. YAMANAKA and A. KATO (1976), Mossbauer effect study of 57Fe and 119Snin stannite, stannoidite and mawsonite. Amer. Mineral. 61, 260-265.

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The superstructure ofstannoidite