Single-crystal investigation of the compound SmNi5.2Mn6.8

Bohdana Belan
  • Chemical Faculty, Ivan Franko National University of Lviv, Kyryla i Mefodiya Street 6, UA-79005 Lviv, Ukraine
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, Dorota Kowalska
  • Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P. O. Box 1410, 50-950 Wrocław, Poland
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, Mykola Manyako
  • Chemical Faculty, Ivan Franko National University of Lviv, Kyryla i Mefodiya Street 6, UA-79005 Lviv, Ukraine
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, Mariya Dzevenko
  • Corresponding author
  • Chemical Faculty, Ivan Franko National University of Lviv, Kyryla i Mefodiya Street 6, UA-79005 Lviv, Ukraine
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and Yaroslav Kalychak
  • Chemical Faculty, Ivan Franko National University of Lviv, Kyryla i Mefodiya Street 6, UA-79005 Lviv, Ukraine
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Abstract

The intermetallic compound SmNi5.2Mn6.8 was synthesized by arc-melting and its crystal structure has been determined using single-crystal X-ray diffraction data. The compound adopts the tetragonal structure type ThMn12: space group I4/mmm, Pearson code tI26, Z = 2; a = 8.6528(3), c = 4.8635(3) Å; R1 = 0.0175, wR2 = 0.0372, 171 F2 values, 17 refined variables. The two crystallographic positions 8f and 8j in the structure of SmNi5.2Mn6.8 are occupied by a mixture of Mn and Ni atoms.

1 Introduction

The structure type ThMn12 [1] is rather widespread among intermetallic compounds. The representatives of this type exist both in the binary systems R-Mn (R=Y, Gd, Tb, Dy, Ho, Er, Tm) [2], [3] and in the ternary systems R-Mn-Т (R=Ce, Pr, Nd, Sm; Т=Fe, Co, Ni) [4], [5]. The transition metals appear to stabilize the compounds with this structure type including the systems with light rare earth metals. The largest number of isotypic compounds have been found in R-T-Al (T=Cr, Mn, Fe, Cu, Re) [6] and R-T-In (T=Cu, Ag) systems [7], while fewer compounds have been reported for related systems with gallium and silicon [6]. The ThMn12 type is characterized by a low content of rare earth metal and high coordination numbers (CN) of all atoms (CN=20 for the Th atoms and CN=12–14 for the Mn atoms). This structure type is closely related to the CаCu5 structure type [8] and can be derived from it by substitution of one R atom by a pair of T component atoms in the unit cell following the scheme: 25=R2Т102Т1012. In cases of strong differences in nature and size of the T component atoms, the atoms can be ordered with the formation of the superstructure type CeMn4Al8 [9]. In our earlier work we found the existence of compounds with the ThMn12 type in R-Mn-{Fe, Co, Ni} systems, but only the values of the cell parameters have been determined for them using powder X-ray diffraction [4], [5]. These compounds can be considered as promising magnetic materials.

Therefore, in this paper we report on the synthesis of high-quality SmNi5.2Mn6.8 single crystals and the determination of the crystal structure of this compound.

2 Experimental details

A sample of nominal composition Sm7.7Ni40Mn52.3 was synthesized from the high-purity elements (Sm≥99.9 wt.%, Ni≥99.92 wt.%, and Mn≥99.90 wt.%) by arc-melting under a purified argon atmosphere, using Ti as a getter and a tungsten electrode. To achieve high efficiency of the interaction between the components, the sample was melted twice. The ingot was annealed at 600°C in an evacuated quartz ampoule for 720 h and subsequently quenched in cold water. The weight loss during the preparation of the sample was less than 1% of the total mass of 2 g.

Laue and rotation diffraction patterns of selected single crystals showed tetragonal symmetry with lattice parameters a~8.6 and c~4.7 Å. Integrated intensities measured at room temperature with graphite-monochromatized MоKα radiation (λ=0.71073 Å) on an Oxford Diffraction Xcalibur four-circle diffractometer equipped with a CCD camera confirmed the tetragonal lattice. Data collection and reduction were made using CrysAlis CCD and CrysAlis Red programs [10] taking into account a numerical absorption correction. The structure was solved by Direct Methods,and refined using the Shelx-2014 program package [11].

The chemical composition of the selected crystals was checked with a field-emission scanning electron microscope (FEINovaNanoSEM 230) equipped with an EDS analyzer (EDAX GenesisXM4, accelerating voltage 20 kV, exposure time 120 s).

Further details of the crystal structure investigation may be obtained from Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany (fax: +49-7247-808-666; e-mail: crysdata@fiz-karlsruhe.de, http://www.fiz-informationsdienste.de/en/DB/icsd/depot_anforderung.html) on quoting the deposition number CSD-1958794.

3 Results and discussion

Analysis of the XRD data collected for SmNi5.2Mn6.8 indicated that the compound crystallizes with a centrosymmetric structure, space group I4/mmm. The structure type ThMn12 was assigned and the structure was refined with anisotropic displacement parameters for all atoms. A final electron density difference map was flat and did not reveal any significant residual peaks. The crystal data and details of the data collection are given in Table 1, while the atomic coordinates and the displacement parameters are listed in Table 2. All crystallographic positions are fully occupied, but the atomic positions 8f and 8j are occupied by a mixture of manganese and nickel atoms with ratios of Mn to Ni of 0.24(3):0.76(3) and 0.46(3):0.54(3), respectively. The refined atomic positions for SmNi5.2Mn6.8 are similar to the respective positions of atoms in the ThMn12 type [1]. The refined composition is in good agreement with the results of the EDX analyses (8 at% Sm: 52 at% Mn: 40 at% Ni).

Table 1:

Crystal data and structure refinement details for SmNi5.2Mn6.8.

Empirical formulaSmNi5.2Mn6.8
Formula weight829.25
Crystal colorBlack
Crystal size, mm30.069×0.035×0.026
Space groupI4/mmm (No. 139)
Pearson codetI26
Unit cell dimensions
a, Å8.6528(3)
c, Å4.8635(3)
 Volume, Å3364.13(3)
 Number of formula units per unit cell2
 Calculated density, g cm−37.56
 Absorption coefficient, mm−132.2
F(000), e755
θ range for data collection3.330–29.970
 Index ranges hkl±11, ±11, ±6
 Reflections collected1955
 Independent reflections/Rint171/0.0277
 Reflections with I>2 σ(I)161
 Refinement methodFull-matrix least-square on F2
 Data/ref. parameters171/17
 Goodness-of-fit on F21.195
 Final indices R1/wR2 [I>2 σ(I)]0.0175/0.0372
 Final indices R1/wR2 (all data)0.0195/0.0387
 Largest diff. peak/hole, e Å−33.31/−0.91
Table 2:

Atomic coordinates and displacement parameters for SmNi5.2Mn6.8.a

AtomWSOccupationxyzUiso
Sm2a10000.0149(2)
Т18f0.24(3)Mn+0.76(3)Ni1/41/41/40.0080(3)
Т28j0.46(3)Mn+0.54(3)Ni0.22011(10)1/200.0098(3)
Mn8i10.35615(10)000.0097(2)
AtomU11U22U33U23U13U12
Sm0.0101(2)U110.0245(4)000
Т10.0090(3)U110.0058(4)0.00087(19)U230.0005(3)
Т20.0064(4)0.0142(5)0.0087(4)000
Mn0.0090(4)0.0086(4)0.0115(4)000

aUiso is defined as one third of the trace of the orthogonalized Uij tensor. The anisotropic displacement factor exponent takes the form: −2π2 (U11h2a*2+U22k2b*2+U33l2c*2+2 U12hka*b*+2 U13hla*c*+2 U23klb*c*).

A projection of the unit cell of SmNi5.2Mn6.8 onto the crystallographic ab plane and the coordination polyhedra of all atoms are shown on Fig. 1. The samarium atom is in the center of a 20-vertex polyhedron [SmMn4Т16] similar to the environment of the thorium atoms in the ThMn12 structure. The smallest atoms in SmNi5.2Mn6.8, i.e. the mixture of Mn/Ni atoms, are located inside the icosahedra [Т1Т6Mn4Sm2] and [Т2Т6Mn4Sm2] with CN=12, while the bigger manganese atoms have 14 neighbors [MnТ8Mn5Sm]. Similar situations have been observed for the compounds ErCu5.1In6.9 [12] and YbAg5.4In6.6 [13], where the bigger In atoms, compared with the mixtures (Cu/In) or (Ag/In), also reside in 14-vertex polyhedra.

Fig. 1:
Fig. 1:

Projection of the unit cell of SmNi5.2Mn6.8 onto the crystallographic ab plane and coordination polyhedra of the atoms.

Citation: Zeitschrift für Naturforschung B 75, 3; 10.1515/znb-2019-0181

The main interatomic distances and their values of reductions orientated at the sum of atomic radii (Δ=100(d−Σr)/Σr, where Σr is the sum of the respective atomic radii) along with the coordination numbers of atoms for SmNi5.2Mn6.8 are listed in Table 3 (values of the atomic radii are taken from ref. [14]: r(Sm)=1.80, r(Ni)=1.24, r(Mn)=1.27, and calculated r(Т1)=1.24 and r(Т2)=1.25 Å). Most deviations of the interatomic distances from the sums of relevant atomic radii are very small (no more than 8%). Some Mn–Mn and Т1–Т1 interatomic distances are slightly shorter compared to the sum of the respective atomic radii. Such shortening of interatomic distances allows us to consider a pairing of the respective atoms. The manganese atoms form dumb-bells, while the Т1 atoms are combined to chains along the c direction. Two Sm atoms, four Mn atoms and 14 T atoms form the coordination sphere of the Mn2 dumb-bells in the SmNi5.2Mn6.8 structure (Fig. 2). Such clusters [Mn2(Sm2Mn4T14)] are connected through common faces and form grids perpendicular to the c direction, in the holes of which the Sm atoms are located. The coordination polyhedra of the Т1 atoms are connected along the c direction to form tubes [Т12(Sm3Mn6T6)] in the middle of which there is the Т1 atom chain (Fig. 3). Further, these tubes are connected through common faces and completely fill the space in the structure of SmNi5.2Mn6.8.

Table 3:

Interatomic distances (d, Å), Δ values (Δ=100(d−Σr)/Σr, where Σr is the sum of the respective atomic radii [13]) and atomic coordination numbers (CN) for SmNi5.2Mn6.8.a

Atomd (Å)Δ (%)Atomd (Å)Δ (%)
Sm4 Mn3.0817(1)0.4T24 Т12.4949(1)0.2
CN=208 Т23.0888(1)1.3CN=122 Т22.6935(9)7.7
8 Т13.2920(1)8.32 Mn2.7017(6)7.2
2 Mn2.7230(11)8.1
2 Sm3.0888(5)1.37
Т12 Т12.4318(2)−1.9Mn1 Mn2.4894(12)−2.0
CN=124 Т22.4949(1)0.2CN=144 Т12.6460(3)5.4
4 Mn2.6460(3)5.42 Т22.7017(6)7.2
2 Sm3.2920(1)8.32 Т22.7230(6)8.1
4 Mn3.0020(5)7.21
1 Sm3.0817(9)0.38

aТ1=0.76(3)Ni+0.24(3) Mn; Т2=0.54(3)Ni+0.45(3)Mn.

Fig. 2:
Fig. 2:

The arrangement of the clusters [Mn2(Sm2Mn4T14)] in the crystal structure of SmNi5.2Mn6.8.

Citation: Zeitschrift für Naturforschung B 75, 3; 10.1515/znb-2019-0181

Fig. 3:
Fig. 3:

The [Т12(Sm3Mn6T6)] tube and the arrangement of these tubes in the crystal structure of SmNi5.2Mn6.8.

Citation: Zeitschrift für Naturforschung B 75, 3; 10.1515/znb-2019-0181

The SmNi5.2Mn6.8 structure can also be considered as a combination of simple fragments: tetragonal motifs of the CeMg2Si2 structure (P4/mmm, a=4.250, c=5.765 Å) [8] and slabs of a hypothetical substructure “Mn4T4” (Fig. 4).

Fig. 4:
Fig. 4:

Packing of Mn4T4 and CeMg2Si2 slabs in the crystal structure of SmNi5.2Mn6.8.

Citation: Zeitschrift für Naturforschung B 75, 3; 10.1515/znb-2019-0181

The results of our investigation together with all previous data [4], [5] indicate that Sm(Mn,Ni)12 forms a homogeneity range with Mn/Ni substitutions. The formula of the compound can be described as SmNi8.10−3.94Mn3.90−8.06. The lattice parameters increase due to substitution of smaller Ni atoms with larger Mn atoms (a=8.465–8.693, c=4.766–4.864 Å).

4 Conclusions

The crystal structure of SmNi5.2Mn6.8 has been investigated by using single crystal X-ray data. This compound forms a tetragonal ThMn12-type unit cell (space group I4/mmm, a=8.6528(3), c=4.8635(3) Å), observed before for the binary phases RMn12 with R=Y, Gd, Tb, Dy, Ho, Er, Tm) [2], [3] and for the ternary systems R-Mn-Т with R=Ce, Pr, Nd, Sm and Т=Fe, Co, Ni [4], [5]. Mixtures of Mn/Ni atoms occupy two crystallographic positions in the structure of this compound while the remaining two positions are occupied solely by Sm and Mn atoms.

References

  • [1]

    J. V. Florio, R. E. Rundle, A. I. Snow, Acta Crystallogr. 19525, 449–457.

  • [2]

    R. L. Myklebust, A. H. Daane, Trans. Metall. Soc. AIME1962224, 354–357.

  • [3]

    F. E. Wang, J. V. Gilfrich, Acta Crystallogr. 196621, 476–481.

  • [4]

    Ya. M. Kalychak, O. I. Bodak, E. I. Gladyshevskii, Sov. Phys. Crystallogr. 197621, 280–282.

  • [5]

    O. I. Bodak, V. K. Pecharskii, Ya. M. Kalychak, O. I. Kharchenko, I. R. Mokra, L. O. Muratova, D. A. Berezyuk, M. M. Shevchuk, Fazovye Ravnovesiya Met. Splavakh, Nauka, Moscow, 1981, p. 57.

  • [6]

    O. I. Bodak, E. I. Gladyshevskii, Rare-Earth-Containing Ternary Systems, Vyshcha Shkola, Lvov, 1985.

  • [7]

    Ya. M. Kalychak, V. I. Zaremba, R. Pöttgen, M. Lukachuk, R.-D. Hoffmann in Handbook on the Physics and Chemistry of Rare Earths, Vol. 34 (Eds.: K. A. Gschneidner Jr., V. K. Pecharsky, J.-C. Bünzli), Elsevier, Amsterdam, 2005, chapter 218, p. 1.

  • [8]

    P. I. Krypyakevich, Structure Types of the Intermetallic Compounds, Nauka, Moscow, 1977.

  • [9]

    E. I. Gladyshevskii, P. I. Krypyakevich, M. Yu. Teslyuk, O. S. Zarechnyuk, Yu. B. Kuz’ma, Kristallographiya19616, 267–268.

  • [10]

    CrysAlis CCD and CrysAlis Red (version 1.171), Intelligent Data Collection and Processing Software for Small Molecule and Protein Crystallography, Rigaku Oxford Diffraction, Yarnton, Oxfordshire (U.K.) 2015.

  • [11]

    G. M. Sheldrick, Acta Crystallogr.2015C71, 3–8.

  • [12]

    L. V. Sysa, Ya. M. Kalychak, A. Bakar, V. M. Baranyak, Kristallographiya198934, 744–745.

  • [13]

    L. V. Sysa, Visnyk Lviv Univ. Ser. Chem. 199131, 15–16.

  • [14]

    J. Emsley, The Elements, (2nd edition), Clarendon Press, Oxford, 1991.

If the inline PDF is not rendering correctly, you can download the PDF file here.

  • [1]

    J. V. Florio, R. E. Rundle, A. I. Snow, Acta Crystallogr. 19525, 449–457.

  • [2]

    R. L. Myklebust, A. H. Daane, Trans. Metall. Soc. AIME1962224, 354–357.

  • [3]

    F. E. Wang, J. V. Gilfrich, Acta Crystallogr. 196621, 476–481.

  • [4]

    Ya. M. Kalychak, O. I. Bodak, E. I. Gladyshevskii, Sov. Phys. Crystallogr. 197621, 280–282.

  • [5]

    O. I. Bodak, V. K. Pecharskii, Ya. M. Kalychak, O. I. Kharchenko, I. R. Mokra, L. O. Muratova, D. A. Berezyuk, M. M. Shevchuk, Fazovye Ravnovesiya Met. Splavakh, Nauka, Moscow, 1981, p. 57.

  • [6]

    O. I. Bodak, E. I. Gladyshevskii, Rare-Earth-Containing Ternary Systems, Vyshcha Shkola, Lvov, 1985.

  • [7]

    Ya. M. Kalychak, V. I. Zaremba, R. Pöttgen, M. Lukachuk, R.-D. Hoffmann in Handbook on the Physics and Chemistry of Rare Earths, Vol. 34 (Eds.: K. A. Gschneidner Jr., V. K. Pecharsky, J.-C. Bünzli), Elsevier, Amsterdam, 2005, chapter 218, p. 1.

  • [8]

    P. I. Krypyakevich, Structure Types of the Intermetallic Compounds, Nauka, Moscow, 1977.

  • [9]

    E. I. Gladyshevskii, P. I. Krypyakevich, M. Yu. Teslyuk, O. S. Zarechnyuk, Yu. B. Kuz’ma, Kristallographiya19616, 267–268.

  • [10]

    CrysAlis CCD and CrysAlis Red (version 1.171), Intelligent Data Collection and Processing Software for Small Molecule and Protein Crystallography, Rigaku Oxford Diffraction, Yarnton, Oxfordshire (U.K.) 2015.

  • [11]

    G. M. Sheldrick, Acta Crystallogr.2015C71, 3–8.

  • [12]

    L. V. Sysa, Ya. M. Kalychak, A. Bakar, V. M. Baranyak, Kristallographiya198934, 744–745.

  • [13]

    L. V. Sysa, Visnyk Lviv Univ. Ser. Chem. 199131, 15–16.

  • [14]

    J. Emsley, The Elements, (2nd edition), Clarendon Press, Oxford, 1991.

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    Projection of the unit cell of SmNi5.2Mn6.8 onto the crystallographic ab plane and coordination polyhedra of the atoms.

  • View in gallery

    The arrangement of the clusters [Mn2(Sm2Mn4T14)] in the crystal structure of SmNi5.2Mn6.8.

  • View in gallery

    The [Т12(Sm3Mn6T6)] tube and the arrangement of these tubes in the crystal structure of SmNi5.2Mn6.8.

  • View in gallery

    Packing of Mn4T4 and CeMg2Si2 slabs in the crystal structure of SmNi5.2Mn6.8.