- Email: [email protected]
The crystal structure of Ni3Sn2S2 and related compounds
185
of the Less-Common Metals, 45 (1976) 185 - 191 0 Elsevier Sequoia S.A., Lausanne - Printed in the Netherlands
Journal
THE CRYSTAL POUNDS
STRUCTURE
OF Ni3Sn,S2
AND RELATED
COM-
ANNICK MICHELET Laboratoire de Chimie Minerale Structurale, Laboratoire associe au C.N.R.S. Facultk des Sciences Pharmaceutiques et Biologiques de Paris V, 4, Avenue vatoire, 75270 Paris Cedex 06 (France)
No. 200, de I’Obser-
GASTON COLLIN Laboratoire Biologiques
de Chimie Minerale et Generule, Faculte des Sciences Pharmaceutiques de Paris XI, Rue J.B. Clement, 92290 Chatenay Malabry (France)
et
(Received June 3, 1975)
Summary
NisSnsSs is monoclinic, space group B2/m(Ct,) with a = 9.331(3), b = 5.403(2), c = 5.458(2) 8, y = 124.55 “(2). This compound is a nickel sulfostannide with each Ni atom surrounded by four Sn and two S atoms. Other compounds with this type of structure are NisB& (B = Pb, Tl, In) and NisPbsSes. NisBisSs presents a different crystal symmetry.
Introduction
Some natural compounds of the general formula NisBsXs were described a number of years ago. Michener and Peacock (1943) [l] first studied parkerite (NisBisSs), to which they ascribed an orthorhombic cell. Peacock and MacAndrew (1950) [2] determined the structure of shandite (NisPbsSs) to be a pseudo-cubic, rhombohedral cell. Hiller (1951) [3] subsequently studied the solid solutions NisPb&, NisPbsSes, and NiaPbsTes, and used the lattice parameters found by Peacock et al. to index the powder patterns. Myuller [4] worked on the Pb-Se-Ni system and found only one ternary phase, NisPbsSes. Finally, in 1973, Fleet [5] re-examined the parkerite (NisBisSs) structure, which he refined in the orthorhombic cell of the space group &am (&) proposed by Michener et al. In the course of a systematic study on the physical, magnetic and electric properties of Ni3B2X2 compounds, we examined some previous results which disagreed with our own observations. 1. The existence
of the compounds
Only the compounds NisPbsS?, NisPbsSes and NisBisSs had been identified. We therefore looked for other NisBzXz-type compounds which con-
186
tamed other elements, and prepared, for the first time, NisTl&, NisInsSs and NisSnsSs. Other attempts in which Hg, Sb, Ge or Ga took the place of the B element led to different phases, i.e., (i) no combination occurred with mercury, (ii) a pyrite-type compound, NisSb&, was formed, (iii) with Ge and Ga, two new phases were found on which work is in progress. (iv) With selenium, only Ni,PbsSes exists. (v) With tellurium we could not obtain any NisBsXs-type compound; in particular, NisBiaTes and NiaSnsTes gave NiAs-type phases. Similarly, substitution of the sulphur by phosphorus did not lead to isotypic compounds. 2. The crystallographic
parameters
The NisBsXs compounds were all prepared in two stages. NisSs or NisSes were first synthesised by direct combination of the elements in evacuated, sealed silica ampoules, at a fusion temperature of 9OO’“C. The Ni,X2 and the B element were then reacted in stoichiometric proportions by melting at 900 ‘C, followed by slow cooling. It was found from the powder patterns of NisBsXa compounds which we prepared: (i) that on the one hand, in agreement with the results of Michener et al. and Fleet, NisBsSs belonged to a crystallographic type different from that of other compounds. This particular compound was not studied further; (ii) that on the other hand, for the other products, no line could be indexed in the rhombohedral system as proposed by Peacock et al. We therefore prepared single crystals of some of these compounds in order to try to determine the unit cells and the crystalline type, and crystals of NisSn& and NisPbsSs were investigated by rotation and Weissenberg photographs. The lattice was found to be monoclinic with only one hkl systematic extinction, for h + 1= 2n + 1. This indicates three possible space groups, Bm, B2, or B2/m. The parameters, refined from powder-pattern lines taken with a Guinier camera, are given in Table 1. It may be recalled that for these compounds a rhombohedr~ pseudocubic cell was proposed by Peacock et al. with the following parameters for NisPbsSs: pseudo-cubic cell = a, = 7.87 kX, rhombohedral cell : aRh = 5.56 kX cx=60”. Our results were compared with those of these authors and we pointed out that there was actually a rhombohedral closed-symmetry which, to be accurate, must satisfy the following relationships: b monoc = c monoc = a rhomb, a monoc = a rhomb X 43, y = 125.25 O.
187 TABLE
1
NisBizXz
compounds
crystal parameters
4a 1
WA1
c(A)
9.331(3) 9.645(4) 9.719( 2) 9.300( 2) 9.472(2)
5.403( 2) 5.577(2) 5.755( 1) 5.484( 2) 5.593( 1)
5.458( 5.602( 5.608( 5.370( 5.469(
Ni$n2S2 Ni,Pb& NiaPbzSez Ni$n$.$ Ni3TQ&
TABLE
2
Powder
diagram
indices
of Ni$n$$
(Guinier
camera,
Y 2) 3) 1) 2) 2)
124.55 125.00 124.24 124.42 124.36
o ’ ’ ’ ’
(2) (3) (2) (2) (2)
CuKol)
.d(a)
Monoclinic (this work)
4.447 4.382
010
3.839
200
111
2.728 2.700
111
002
3il
220
2.328 2.319
301 210
121 012
2.225 2.194
020
202
420
1.922
400
222
521 4i2
450 230
1.725 1.710
311 5il
022 422
1.575 1.573 1.556
220
113
402 620
181 591
1.759 1.748
indices
Rhombohedral indices (Michener et al. )
001
111
2io
t 002
1 I 2i2
1
t
022
113
222
133
1 ii3 331
024
224 323
I
It may be observed that these conditions are almost realized in the NisPbzSz compound; this may explain the difficulties met formerly by Peacock and MacAndrew. On the other hand, the parameters of other products deviate very perceptibly from rhombohedral requirements, and we can only index them in the monoclinic system proposed. NisSnzSz powder-pattern line-indices in the monoclinic system, and those calculated on a rhombohedral basis, are given in Table 2. This table
Fig. 1. Transition from the rhombohedral pseudo-cubic cell to the monoclinic.
shows clearly that distinct lines are confused in the rhombohedral system. This establishes, therefore, that these compounds are actually monoclinic. 3. The NiaSnzSz crystal structure For a structural study, we chose NisSnzSz. Good quality single crystals were obtained quite easily by slowly cooling a molten mixture of Ni& + 2Sn. In this compound, the presence of tin atoms (atomic number, 2, = 50) is more suitable for the determination of the position of the light atoms, Ni and S, than is lead (2 = 82). Unit cell parameters are: a = 9.331(3) A b = 5.403(2) A c = 5.458(2) A y = 124.55(2) o Z= 2. A single crystal, 0.240 X 0.112 X 0.080 mm (the longest dimension being the monoclinic c axis), was mounted on a Syntex P2r four-circle diffractometer. 387 reflections were measured by the 28 scan technique using molybdenum Ka radiation. The total range of 20 for reflections was 0 - 60 O. After Lorentz and polarization corrections, 371 reflections with 12 30 were retained for refinement. The three-dimensional Patterson function calculated, showed that all the atoms were located in centrosymmetric space group’B2lm (C&) special positions. After refining with anisotropic thermal parameters the last R factor reached a value of 0.040 for the atomic positions and thermal factors given in Table 3. The description of this structure shows that this compound can be considered as being a nickel sulfostannide. The nickel atoms, Ni(1) and Ni(II), are located in identical six-coordinated sites, each being surrounded by four tin atoms and by two sulphur atoms. Ni-Sn and Ni-S distances are given in Table 4. Ni(S&ln,) octahedra are regular, the nickel atoms being centered inside a rectangle of four Sn atoms, and the two Ni-S bonds are perpendicu
189
Fig. 2. NiaSn#z structure. Sulfur atoms are open circles, nickel atoms are black, and tin atoms are hatched. Fig. 3. Ni environment. Sulphur atoms open circles, tin atoms hatched. TABLE 4 Ni-Sn and Ni-S bond lengths in Ni$%$$ Bonds
Number of equivalent bonds
Distances (A)
Ni(IbSn(1) Ni(IkSn(I1) Ni( 1)-S
2 2 2
2.13 2.70 2.19
Ni(II)-Sn(1) Ni( II)-Sn( II) Ni( 11)-S
2 2 2
2.73 2.70 2.19
lar to this NiSn4 plane. Ni-Sn distances are a little longer than those observed in NiSn, which has the NiAs distorted type (2.6 A) [6]. On the other hand, the Ni-S distances are slightly shorter than the average in nickel sulfides (approx. 2.3 A) and are equivalent to those found in e-N&S, (Fleet, 1972) [7] and millerite type NiS, 2.15 and 2.19 A, respectively. The shortest Ni-Ni distances, equal to 2.73 8, for Ni(I)-Ni(1) and, similarly, 2.73 A for Ni(I)-Ni(II) are longer than those observed in metallic Ni (2.492 A), and do not correspond to Ni-Ni bonds, they are, however, short enough to indicate a certain degree of d-orbital interaction.
191 TABLE 5 Sn-Ni and Sn-S bond lengths in NiaSn$& .-__IcBonds
Number of equivalent bonds
~-
Distances (A)
Sn( I)-Ni( I) Sn(I~Ni(I1) %-ifI)-S
4 2 2
2.73 2.73 2.37
Sn( II)-Ni(1) Sn( II)-Ni( II) -_
4 2
2.70 2.70
Every tin atom is coordina~d to six nickel atoms (Table 5). Rut Sn(1) forms two Sn-S bonds, while the shortest Ni(II)-S are 3.22 a long and cannot be considered as actual bonds. Around Sn(I), the six Ni atoms are positioned in a plane and form a practic~ly perfect hexagon, the two Sn-S bonds being pe~endicul~ to this plane. In addition, Sn(I1) atoms are in the center of a rectangle of four Ni(1) atoms, the two Sn~II)-Ni(I1) bonds being on both sides of this plane. Sn-S distances are longer than those observed in SnS and SnS2 (2.62 A) IS], and S-S distances are 3.43 a and correspond to S2--S2contacts. Therefore, this compound behaves as a sulfostannide, S and Sn behaving as anions around Ni atoms, with bonds similar to those observed in NiS and NiSn. Each NiS2Sn, octahedron shares a common Sn2S face with four octahedra and is linked to six other octahedra by means of apical Sn atoms, It is, therefore, a typical 3-Dimensions structure with respect to the Ni atoms. In conclusion, the NiaSnaS2 (and isostructur~ compounds) structure has been presented so as to allow an accurate inte~retati~n of the properties, at present being studied on single crystals, which behave like metals with very weak magnetic moments (as compared with the nickel atom). References 1 2 3 4 5 6 7 8
C. E. Michener and M. A. Peacock, Am. Mineral., 28 (1943) 343 ” 366. M. A. Peacock and J. MaeAndrew, Am. Mineral., 35 (1950) 425 - 439. J. E. Hiller, Neues Jahrb. Mineral. Monatsh., (1951) 265 - 277. N. M. Myulier and L. I. Sotnikova, izv. Akad. Nauk SSSR, Inorg. Mater., 5 (II) (1969). M. E. Fleet, Am. Mineral., 58 (1973) 435 - 439. M. K. Bhargava and K. J. Schubert, J: Less-Common Met., 33 (1973) 181 - 189. M. E. Fleet, Acta Crystallogr. B, 28 (1972) 1237 - 1247. W. Z. Hofmann, Kristallografia, 92 (1935) 161.
of the Less-Common Metals, 45 (1976) 185 - 191 0 Elsevier Sequoia S.A., Lausanne - Printed in the Netherlands
Journal
THE CRYSTAL POUNDS
STRUCTURE
OF Ni3Sn,S2
AND RELATED
COM-
ANNICK MICHELET Laboratoire de Chimie Minerale Structurale, Laboratoire associe au C.N.R.S. Facultk des Sciences Pharmaceutiques et Biologiques de Paris V, 4, Avenue vatoire, 75270 Paris Cedex 06 (France)
No. 200, de I’Obser-
GASTON COLLIN Laboratoire Biologiques
de Chimie Minerale et Generule, Faculte des Sciences Pharmaceutiques de Paris XI, Rue J.B. Clement, 92290 Chatenay Malabry (France)
et
(Received June 3, 1975)
Summary
NisSnsSs is monoclinic, space group B2/m(Ct,) with a = 9.331(3), b = 5.403(2), c = 5.458(2) 8, y = 124.55 “(2). This compound is a nickel sulfostannide with each Ni atom surrounded by four Sn and two S atoms. Other compounds with this type of structure are NisB& (B = Pb, Tl, In) and NisPbsSes. NisBisSs presents a different crystal symmetry.
Introduction
Some natural compounds of the general formula NisBsXs were described a number of years ago. Michener and Peacock (1943) [l] first studied parkerite (NisBisSs), to which they ascribed an orthorhombic cell. Peacock and MacAndrew (1950) [2] determined the structure of shandite (NisPbsSs) to be a pseudo-cubic, rhombohedral cell. Hiller (1951) [3] subsequently studied the solid solutions NisPb&, NisPbsSes, and NiaPbsTes, and used the lattice parameters found by Peacock et al. to index the powder patterns. Myuller [4] worked on the Pb-Se-Ni system and found only one ternary phase, NisPbsSes. Finally, in 1973, Fleet [5] re-examined the parkerite (NisBisSs) structure, which he refined in the orthorhombic cell of the space group &am (&) proposed by Michener et al. In the course of a systematic study on the physical, magnetic and electric properties of Ni3B2X2 compounds, we examined some previous results which disagreed with our own observations. 1. The existence
of the compounds
Only the compounds NisPbsS?, NisPbsSes and NisBisSs had been identified. We therefore looked for other NisBzXz-type compounds which con-
186
tamed other elements, and prepared, for the first time, NisTl&, NisInsSs and NisSnsSs. Other attempts in which Hg, Sb, Ge or Ga took the place of the B element led to different phases, i.e., (i) no combination occurred with mercury, (ii) a pyrite-type compound, NisSb&, was formed, (iii) with Ge and Ga, two new phases were found on which work is in progress. (iv) With selenium, only Ni,PbsSes exists. (v) With tellurium we could not obtain any NisBsXs-type compound; in particular, NisBiaTes and NiaSnsTes gave NiAs-type phases. Similarly, substitution of the sulphur by phosphorus did not lead to isotypic compounds. 2. The crystallographic
parameters
The NisBsXs compounds were all prepared in two stages. NisSs or NisSes were first synthesised by direct combination of the elements in evacuated, sealed silica ampoules, at a fusion temperature of 9OO’“C. The Ni,X2 and the B element were then reacted in stoichiometric proportions by melting at 900 ‘C, followed by slow cooling. It was found from the powder patterns of NisBsXa compounds which we prepared: (i) that on the one hand, in agreement with the results of Michener et al. and Fleet, NisBsSs belonged to a crystallographic type different from that of other compounds. This particular compound was not studied further; (ii) that on the other hand, for the other products, no line could be indexed in the rhombohedral system as proposed by Peacock et al. We therefore prepared single crystals of some of these compounds in order to try to determine the unit cells and the crystalline type, and crystals of NisSn& and NisPbsSs were investigated by rotation and Weissenberg photographs. The lattice was found to be monoclinic with only one hkl systematic extinction, for h + 1= 2n + 1. This indicates three possible space groups, Bm, B2, or B2/m. The parameters, refined from powder-pattern lines taken with a Guinier camera, are given in Table 1. It may be recalled that for these compounds a rhombohedr~ pseudocubic cell was proposed by Peacock et al. with the following parameters for NisPbsSs: pseudo-cubic cell = a, = 7.87 kX, rhombohedral cell : aRh = 5.56 kX cx=60”. Our results were compared with those of these authors and we pointed out that there was actually a rhombohedral closed-symmetry which, to be accurate, must satisfy the following relationships: b monoc = c monoc = a rhomb, a monoc = a rhomb X 43, y = 125.25 O.
187 TABLE
1
NisBizXz
compounds
crystal parameters
4a 1
WA1
c(A)
9.331(3) 9.645(4) 9.719( 2) 9.300( 2) 9.472(2)
5.403( 2) 5.577(2) 5.755( 1) 5.484( 2) 5.593( 1)
5.458( 5.602( 5.608( 5.370( 5.469(
Ni$n2S2 Ni,Pb& NiaPbzSez Ni$n$.$ Ni3TQ&
TABLE
2
Powder
diagram
indices
of Ni$n$$
(Guinier
camera,
Y 2) 3) 1) 2) 2)
124.55 125.00 124.24 124.42 124.36
o ’ ’ ’ ’
(2) (3) (2) (2) (2)
CuKol)
.d(a)
Monoclinic (this work)
4.447 4.382
010
3.839
200
111
2.728 2.700
111
002
3il
220
2.328 2.319
301 210
121 012
2.225 2.194
020
202
420
1.922
400
222
521 4i2
450 230
1.725 1.710
311 5il
022 422
1.575 1.573 1.556
220
113
402 620
181 591
1.759 1.748
indices
Rhombohedral indices (Michener et al. )
001
111
2io
t 002
1 I 2i2
1
t
022
113
222
133
1 ii3 331
024
224 323
I
It may be observed that these conditions are almost realized in the NisPbzSz compound; this may explain the difficulties met formerly by Peacock and MacAndrew. On the other hand, the parameters of other products deviate very perceptibly from rhombohedral requirements, and we can only index them in the monoclinic system proposed. NisSnzSz powder-pattern line-indices in the monoclinic system, and those calculated on a rhombohedral basis, are given in Table 2. This table
Fig. 1. Transition from the rhombohedral pseudo-cubic cell to the monoclinic.
shows clearly that distinct lines are confused in the rhombohedral system. This establishes, therefore, that these compounds are actually monoclinic. 3. The NiaSnzSz crystal structure For a structural study, we chose NisSnzSz. Good quality single crystals were obtained quite easily by slowly cooling a molten mixture of Ni& + 2Sn. In this compound, the presence of tin atoms (atomic number, 2, = 50) is more suitable for the determination of the position of the light atoms, Ni and S, than is lead (2 = 82). Unit cell parameters are: a = 9.331(3) A b = 5.403(2) A c = 5.458(2) A y = 124.55(2) o Z= 2. A single crystal, 0.240 X 0.112 X 0.080 mm (the longest dimension being the monoclinic c axis), was mounted on a Syntex P2r four-circle diffractometer. 387 reflections were measured by the 28 scan technique using molybdenum Ka radiation. The total range of 20 for reflections was 0 - 60 O. After Lorentz and polarization corrections, 371 reflections with 12 30 were retained for refinement. The three-dimensional Patterson function calculated, showed that all the atoms were located in centrosymmetric space group’B2lm (C&) special positions. After refining with anisotropic thermal parameters the last R factor reached a value of 0.040 for the atomic positions and thermal factors given in Table 3. The description of this structure shows that this compound can be considered as being a nickel sulfostannide. The nickel atoms, Ni(1) and Ni(II), are located in identical six-coordinated sites, each being surrounded by four tin atoms and by two sulphur atoms. Ni-Sn and Ni-S distances are given in Table 4. Ni(S&ln,) octahedra are regular, the nickel atoms being centered inside a rectangle of four Sn atoms, and the two Ni-S bonds are perpendicu
189
Fig. 2. NiaSn#z structure. Sulfur atoms are open circles, nickel atoms are black, and tin atoms are hatched. Fig. 3. Ni environment. Sulphur atoms open circles, tin atoms hatched. TABLE 4 Ni-Sn and Ni-S bond lengths in Ni$%$$ Bonds
Number of equivalent bonds
Distances (A)
Ni(IbSn(1) Ni(IkSn(I1) Ni( 1)-S
2 2 2
2.13 2.70 2.19
Ni(II)-Sn(1) Ni( II)-Sn( II) Ni( 11)-S
2 2 2
2.73 2.70 2.19
lar to this NiSn4 plane. Ni-Sn distances are a little longer than those observed in NiSn, which has the NiAs distorted type (2.6 A) [6]. On the other hand, the Ni-S distances are slightly shorter than the average in nickel sulfides (approx. 2.3 A) and are equivalent to those found in e-N&S, (Fleet, 1972) [7] and millerite type NiS, 2.15 and 2.19 A, respectively. The shortest Ni-Ni distances, equal to 2.73 8, for Ni(I)-Ni(1) and, similarly, 2.73 A for Ni(I)-Ni(II) are longer than those observed in metallic Ni (2.492 A), and do not correspond to Ni-Ni bonds, they are, however, short enough to indicate a certain degree of d-orbital interaction.
191 TABLE 5 Sn-Ni and Sn-S bond lengths in NiaSn$& .-__IcBonds
Number of equivalent bonds
~-
Distances (A)
Sn( I)-Ni( I) Sn(I~Ni(I1) %-ifI)-S
4 2 2
2.73 2.73 2.37
Sn( II)-Ni(1) Sn( II)-Ni( II) -_
4 2
2.70 2.70
Every tin atom is coordina~d to six nickel atoms (Table 5). Rut Sn(1) forms two Sn-S bonds, while the shortest Ni(II)-S are 3.22 a long and cannot be considered as actual bonds. Around Sn(I), the six Ni atoms are positioned in a plane and form a practic~ly perfect hexagon, the two Sn-S bonds being pe~endicul~ to this plane. In addition, Sn(I1) atoms are in the center of a rectangle of four Ni(1) atoms, the two Sn~II)-Ni(I1) bonds being on both sides of this plane. Sn-S distances are longer than those observed in SnS and SnS2 (2.62 A) IS], and S-S distances are 3.43 a and correspond to S2--S2contacts. Therefore, this compound behaves as a sulfostannide, S and Sn behaving as anions around Ni atoms, with bonds similar to those observed in NiS and NiSn. Each NiS2Sn, octahedron shares a common Sn2S face with four octahedra and is linked to six other octahedra by means of apical Sn atoms, It is, therefore, a typical 3-Dimensions structure with respect to the Ni atoms. In conclusion, the NiaSnaS2 (and isostructur~ compounds) structure has been presented so as to allow an accurate inte~retati~n of the properties, at present being studied on single crystals, which behave like metals with very weak magnetic moments (as compared with the nickel atom). References 1 2 3 4 5 6 7 8
C. E. Michener and M. A. Peacock, Am. Mineral., 28 (1943) 343 ” 366. M. A. Peacock and J. MaeAndrew, Am. Mineral., 35 (1950) 425 - 439. J. E. Hiller, Neues Jahrb. Mineral. Monatsh., (1951) 265 - 277. N. M. Myulier and L. I. Sotnikova, izv. Akad. Nauk SSSR, Inorg. Mater., 5 (II) (1969). M. E. Fleet, Am. Mineral., 58 (1973) 435 - 439. M. K. Bhargava and K. J. Schubert, J: Less-Common Met., 33 (1973) 181 - 189. M. E. Fleet, Acta Crystallogr. B, 28 (1972) 1237 - 1247. W. Z. Hofmann, Kristallografia, 92 (1935) 161.