inorganic compounds
Redetermination of the distorted perovskite Nd_{0.53}Sr_{0.47}MnO_{3}
^{a}Graduate School of Materials Science & Engineering, Nagoya Institute of Technology, Gokisocho, Showaku, Japan, ^{b}Photon Factory, IMSS, High Energy Accelerator Research Organization (KEK), Tsukuba, 3050801, Japan, and ^{c}Materials Structure Physics Group, Department of Physics, Graduate School of Science, Tohoku University, Sendai 9808578, Japan
^{*}Correspondence email: 14515020@stn.nitech.ac.jp
Neodymium strontium manganese oxide with ideal composition Nd_{0.5}Sr_{0.5}MnO_{3} was reported to have two different structure models. In one model, the x coordinate of an O atom is at x > 1/2, while in the other model the xcoordinate of this atom is at x < 1/2. Differencedensity maps around this O atom obtained from the current redetermination clearly show that the structure with the O atom at x < 1/2 result in a more satisfactory model than that with x > 1/2. The title compound with a refined composition of Nd_{0.53 (5)}Sr_{0.47 (5)}MnO_{3} is a distorted perovskitetype structure with site symmetries 2mm for the statistically occupied (Nd, Sr) site and for the abovementioned O atom, .2/m. for the Mn atom and ..2 for a second Oatom site. In contrast to previous studies, the displacement factors for all atoms were refined anisotropically.
Related literature
For details of the synthesis, see: Nakamura et al. (1999). For previous refinements of compounds with composition Nd_{0.5}Sr_{0.5}MnO_{3} from powder and singlecrystal data, see: Woodward et al. (1998), Caignaert et al. (1998) and Kajimoto et al. (1999), Angappane et al. (2004), respectively. For general background, see: Becker & Coppens (1975); Dawson et al. (1967); Libermann et al. (1971); Mann (1968), Tanaka & Marumo (1983).
Experimental
Crystal data

Refinement

Data collection: MXCSYS (MAC Science, 1995) and IUANGLE (Tanaka et al., 1994).; cell RSLC3 UNICS system (Sakurai & Kobayashi, 1979); data reduction: RDEDIT (Tanaka, 2008); program(s) used to solve structure: QNTAO (Tanaka & Ōnuki, 2002; Tanaka et al., 2008); program(s) used to refine structure: QNTAO; molecular graphics: ATOMS for Windows (Dowty, 2000); software used to prepare material for publication: RDEDIT.
Supporting information
10.1107/S1600536808034168/wm2198sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808034168/wm2198Isup2.hkl
A large single crystal was grown using a floating zone method (Nakamura et al., 1999). The bulk sample was put on a piece of filter paper and was etched by diluted nitric acid under a microscope. Finally, the sample was shaped into a 0.040 mm × 0.053 mm × 0.065 mm block. Nd_{0.45}Sr_{0.55}MnO_{3} exhibits a first order
at T_{N} = 225K. The present diffraction study was carried out at 241 (1) K close to the temperature.The structure of Nd_{1 }_{x}Sr_{x}MnO_{3} changes with the holeconcentration x. In the region x > 0.55 the structure has tetragonal symmetry. However, at x = 0.60 a phase with monoclinic symmetry was reported at low temperature (Kajimoto et al. , 1999). Below x = 0.55 it changes to orthorhombic symmetry. Since crystals with monoclinic, orthorhombic and tetragonal symmetries were found in preliminary experiments for crystal with approximate compositions of Nd_{0.45}Sr_{0.55}MnO_{3} (which is expected from the composition of the starting materials), the holeconcentration x (i.e. site occupation factors) were also refined besides the atomic coordinates and the temperature factors. The previous studies (Woodward et al. (1998); Caignaert et al. (1998); Angappane et al. (2004)) have used the standard setting of
No. 74 in Imma. We decided to refine the structure with the setting in Ibmm, because in the orthorhombic phase the crystal axis is taken along the same direction as that of the tetragonal phase which is also adopted by many other physicists to make clear the relationships between the two phases. Furthermore, Nd_{0.45}Sr_{0.55}MnO_{3} is well known as having dx^{2}y^{2} type orbitalordering of Mn and the physical and chemical properties are discussed based on the Ibmm setting.When the coordinates by Caignaert et al. (1998) were used as starting parameters for
the xcoordinate of O1 converged to 0.518 (1) with a Rfactor of 0.0381. Fig. 2 (a) shows the difference density map onto (010) after this in the range 0< z < 1/2 and 0 < x < 1 with the vertical and horizontal lengths of 3.80 Å × 5.48 Å. The cores of Nd/Sr, Mn and O1 are at (0, 1/4), (1/2, 1/2) and (0.52, 1/4). Since there are two high peaks at x = 0.45 and 0.55 in Fig 2 (a), O1 was split into O1(1) at x=0.45 and O1(2) at x=0.55. The site occupation factors of O1(1) and O1(2) became 0.96 (6) and 0.04 (6) after the Hence O1 was concluded to be located only at x=0.45. After the subsequent the Rfactor converged at 0.0289 and the difference density map became likewise more satisfactory (Fig. 2(b)).Although the temperature factor U^{33} of O1 is 0.001 (1) Å^{2} and almost insignificant, it becomes 0.0015 (2) Å^{2} after the
of anharmonic vibration parameters (Dawson et al., 1967; Tanaka & Marumo, 1983) as well as the harmonic ones. Finally, of the site occupation factors revealed a holeconcentration x of 0.47 (5) thus leading to a composition of Nd_{0.53}Sr_{0.47}MnO_{3}.Data collection: MXCSYS (MAC Science, 1995) and IUANGLE (Tanaka et al., 1994).; cell
RSLC3 UNICS system (Sakurai & Kobayashi, 1979); data reduction: RDEDIT (Tanaka, 2008); program(s) used to solve structure: QNTAO (Tanaka & Onuki, 2002; Tanaka et al., 2008); program(s) used to refine structure: QNTAO (Tanaka & Onuki, 2002; Tanaka et al., 2008); molecular graphics: ATOMS for Windows (Dowty, 2000); software used to prepare material for publication: RDEDIT (Tanaka, 2008).Nd_{0.53}Sr_{0.47}MnO_{3}  F(000) = 394.64 
M_{r} = 218.81  D_{x} = 6.479 Mg m^{−}^{3} 
Orthorhombic, Ibmm  Mo Kα radiation, λ = 0.71073 Å 
Hall symbol: I 2c 2c  Cell parameters from 30 reflections 
a = 5.4785 (3) Å  θ = 35.6–37.8° 
b = 5.4310 (3) Å  µ = 28.37 mm^{−}^{1} 
c = 7.6006 (5) Å  T = 241 K 
V = 226.14 (2) Å^{3}  Block, black 
Z = 4  0.07 × 0.05 × 0.04 mm 
MAC Science M06XHF22 fourcircle diffractometer  966 independent reflections 
Radiation source: finefocus rotating anode  679 reflections with F > 3σ(F) 
Graphite monochromator  R_{int} = 0.022 
Detector resolution: 1.25x1.25° pixels mm^{1}  θ_{max} = 74.7°, θ_{min} = 5.3° 
integrated intensities data fom ω/2θ scans  h = −12→14 
Absorption correction: numerical (CCDABS; Zhurov & Tanaka, 2003)  k = −12→14 
T_{min} = 0.358, T_{max} = 0.521  l = −18→18 
1255 measured reflections 
Refinement on F  14 restraints 
Leastsquares matrix: full  Weighting scheme based on measured s.u.'s 
R[F^{2} > 2σ(F^{2})] = 0.028  (Δ/σ)_{max} = 0.00024 
wR(F^{2}) = 0.066  Δρ_{max} = 2.17 e Å^{−}^{3} 
S = 1.19  Δρ_{min} = −3.38 e Å^{−}^{3} 
927 reflections  Extinction correction: B–C type 1 Gaussian anisotropic (Becker & Coppens, 1975) 
65 parameters  Extinction coefficient: 0.029E04 (1) 
Nd_{0.53}Sr_{0.47}MnO_{3}  V = 226.14 (2) Å^{3} 
M_{r} = 218.81  Z = 4 
Orthorhombic, Ibmm  Mo Kα radiation 
a = 5.4785 (3) Å  µ = 28.37 mm^{−}^{1} 
b = 5.4310 (3) Å  T = 241 K 
c = 7.6006 (5) Å  0.07 × 0.05 × 0.04 mm 
MAC Science M06XHF22 fourcircle diffractometer  966 independent reflections 
Absorption correction: numerical (CCDABS; Zhurov & Tanaka, 2003)  679 reflections with F > 3σ(F) 
T_{min} = 0.358, T_{max} = 0.521  R_{int} = 0.022 
1255 measured reflections 
R[F^{2} > 2σ(F^{2})] = 0.028  65 parameters 
wR(F^{2}) = 0.066  14 restraints 
S = 1.19  Δρ_{max} = 2.17 e Å^{−}^{3} 
927 reflections  Δρ_{min} = −3.38 e Å^{−}^{3} 
Experimental. Multiple diffraction was avoided by ψscan. Intensities was measured at equitemperature region of combinaion of angles ω and χ of fourcircle diffractometer 
Refinement. B—C anisotropic type1 extinction parameters (× 10 ^{4}s) are as follows 4087 (526) 6631 (1159) 3088 (391) 790 (416) 1835 (361) 3716 (625) Dawson et al. (1967) proposed the treatment of temperature factors including anharmonic thermal vibration (AHV) effect for highsymmetry crystals by means of series expansion of an oneparticlepotential. Tanaka and Marumo (1983) generalized the treatment and anharmonic third and fourth order parameters were refined in the leastsquare program. AHV parameters were restricted by the site symmetry of Nd/Sr(2 mm), Mn(.2/m.), O1(2 mm) and O2(..2). The anharmonic potentials (V) are represented by the following equation: V_{Nd,Sr,O1}=c_{111}u_{1}^{3}+c_{123}u_{1}u_{2}^{2}+c_{133}u_{1}u_{3}^{2}+q_{1111}u_{1}^{4} +q_{1122}u_{1}^{2}u_{2}^{2}+q_{1133}u_{1}^{2}u_{3}^{2}+q_{2222}u_{2}^{4} +q_{2233}u_{2}^{2}u_{3}^{2}+q_{3333}u_{3}^{4} ···(1) V_{Mn}=q_{1111}u_{1}^{4}+q_{1122}u_{1}^{2}u_{2}^{2}+q_{1133}u_{1}^{2}u_{3}^{2} +q_{2222}u_{2}^{4}+q_{2233}u_{2}^{2}u_{3}^{2}+q_{3333}u_{3}^{4}+q_{1131}u_{1}^{3}u_{3} +q_{2231}u_{2}^{2}u_{1}u_{3}+q_{3331}u_{3}^{3}u_{1} ···(2) V_{O2}=c_{211}u_{1}^{2}u_{2}+c_{222}u_{2}^{3}+c_{233}u_{3}^{2}u_{2}+c_{123}u_{1}u_{2}u_{3} +q_{1111}u_{1}^{4}+q_{1122}u_{1}^{2}u_{2}^{2}+q_{1133}u_{1}^{2}u_{3}^{2} +q_{2222}u_{2}^{4}+q_{2233}u_{2}^{2}u_{3}^{2}+q_{3333}u_{3}^{4}+q_{1131}u_{1}^{3}u_{3} +q_{2231}u_{2}^{2}u_{1}u_{3}+q_{3331}u_{3}^{3}u_{1} ···(3) where (u_{1},u_{2},u_{3}) is a displacement vector from equilibrium position of each atom. The displacement vector of Nd, Sr, O1 was defined on the coordinate system with axes parallel to the crystal axes, a, b and c. That of Mn and O2 was defined by equation (4) and (5) in terms of the lattice vectors a, b and c in the present study. u_{1}= 0.18253a, u_{2}= 0.18413b, u_{3}= 0.13157c ···(4) u_{1}= 0.11080a0.14633b, u_{2}= 0.13157c, u_{3}= 0.14506a + 0.11177b ···(5) Since there is strong correlation between harmonic temperature factors and AHV parameters, the AHV parameters and the harmonic temperature factors were refined alternately. The significant AHV parameters c_{ijk} (× 10^{19}JÅ^{3}) and q_{iijk} (× 10^{19}JÅ^{3}) are as follows: Nd and Sr; c_{111}= 5.9 (49), c_{122}= 3.8 (14), Mn; q_{2231}= 1832 (1560), O1: q_{2222}= 9.5 (39), q_{2233}= 569.9 (2279), O2: c_{211}= 3.7 (33), c_{233}= 0.8 (7), c_{123}= 5.5 (23), q_{2233}= 9.1 (79), 
x  y  z  U_{iso}*/U_{eq}  Occ. (<1)  
Nd  −0.00656 (9)  0  0.25  0.00637 (4)  0.53 (5) 
Sr  −0.00656 (9)  0  0.25  0.00637 (4)  0.47 (5) 
Mn  0.5  0  0  0.00305 (7)  
O1  0.4499 (8)  0  0.25  0.0112 (6)  
O2  0.75  0.25  0.0276 (4)  0.0139 (5) 
U^{11}  U^{22}  U^{33}  U^{12}  U^{13}  U^{23}  
Nd  0.00653 (6)  0.00685 (7)  0.00574 (8)  0  0  0 
Sr  0.00663 (6)  0.00685 (7)  0.00574 (8)  0  0  0 
Mn  0.0035 (1)  0.0030 (1)  0.0027 (1)  0  0  0 
O1  0.015 (1)  0.017 (1)  0.0015 (2)  0  0  0 
O2  0.0148 (7)  0.0116 (7)  0.015 (1)  −0.0058 (6)  0  0 
Mn—O1  1.9199 (6)  Nd^{ii}—O2  2.545 (2) 
Mn—O2  1.9400 (4)  O1—O2  2.721 (3) 
Nd^{i}—Nd^{ii}  3.8064 (5)  Nd^{i}—Mn  3.3043 (4) 
Nd^{ii}—O1^{ii}  2.501 (4)  O1^{iii}—O2^{ii}  2.738 (3) 
Nd^{i}—O2  2.545 (2)  O1—O1^{ii}  3.489 (4) 
Nd^{ii}—O1  2.7332 (5)  O2—O2^{iii}  3.8799 (5) 
Nd^{i}—O1  2.978 (4)  
Nd^{ii}—Nd^{i}—Mn  55.020 (8)  Nd^{i}—O1—Mn  81.8 (1) 
Mn—Nd^{i}—O1  35.10 (8)  Nd^{ii}—O1—Mn  89.07 (3) 
Nd^{i}—Nd^{ii}—Mn  54.769 (6)  Mn—O1—O1^{ii}  95.15 (9) 
Nd^{i}—Nd^{ii}—O2  41.61 (5)  Nd^{ii}—O1^{ii}—O1  51.11 (8) 
Mn—Nd^{ii}—O1^{ii}  89.4 (1)  Nd^{i}—O2—Nd^{ii}  96.8 (1) 
O1—Nd^{ii}—O1^{ii}  83.5 (1)  Nd^{i}—O2—O2^{iii}  144.59 (7) 
O1^{ii}—Nd^{ii}—O2  121.6 (1)  Nd^{ii}—O2—O2^{iii}  47.83 (1) 
Nd^{i}—Mn—Nd^{ii}  70.212 (7)  Nd^{ii}—Nd^{i}—O2  41.61 (5) 
Nd^{ii}—Mn—O1  55.54 (2)  O1—Nd^{i}—O2  58.4 (1) 
Nd^{i}—O1—Nd^{ii}  83.48 (9)  Nd^{i}—Nd^{ii}—O1^{ii}  134.5 (1) 
Nd^{i}—O1—O2  52.83 (8)  Mn—Nd^{ii}—O1  35.39 (1) 
Nd^{ii}—O1—O2  55.64 (6)  Mn—Nd^{ii}—O2^{iii}  87.76 (5) 
O1^{ii}—O1—O2  89.48 (6)  O1—Nd^{ii}—O2^{iii}  114.44 (5) 
O1—O1^{ii}—O2^{iii}  97.8 (1)  O2—Nd^{ii}—O2^{iii}  91.19 (7) 
Nd^{i}—O2—O1  68.77 (9)  Nd^{i}—Mn—O2  50.22 (1) 
Nd^{ii}—O2—O1  62.42 (8)  Nd^{i}—O1—O1^{ii}  128.89 (6) 
Nd^{ii}—Nd^{i}—O1  45.51 (8)  Nd^{ii}—O1—O1^{ii}  45.41 (5) 
Mn—Nd^{i}—O2  35.85 (5)  Mn—O1—O2  45.48 (6) 
Nd^{i}—Nd^{ii}—O1  51.01 (1)  Nd^{ii}—O1^{ii}—O2^{iii}  66.4 (1) 
Nd^{i}—Nd^{ii}—O2^{iii}  132.79 (5)  Nd^{i}—O2—Mn  93.92 (6) 
Mn—Nd^{ii}—O2  35.71 (5)  Nd^{ii}—O2—Mn  94.32 (6) 
O1—Nd^{ii}—O2  61.94 (5)  Mn—O2—O2^{iii}  88.84 (2) 
O1^{ii}—Nd^{ii}—O2^{iii}  60.7 (1)  O1—O2—O2^{iii}  89.42 (6) 
Nd^{i}—Mn—O1  63.12 (2)  O1^{ii}—O2^{iii}—O2  81.49 (5) 
Nd^{ii}—Mn—O2  49.98 (1)  Nd^{ii}—O2^{iii}—O1^{ii}  52.84 (6) 
Symmetry codes: (i) x+1, y, z; (ii) −x+1/2, y+1/2, z; (iii) x−1/2, y+1/2, −z. 
Experimental details
Crystal data  
Chemical formula  Nd_{0.53}Sr_{0.47}MnO_{3} 
M_{r}  218.81 
Crystal system, space group  Orthorhombic, Ibmm 
Temperature (K)  241 
a, b, c (Å)  5.4785 (3), 5.4310 (3), 7.6006 (5) 
V (Å^{3})  226.14 (2) 
Z  4 
Radiation type  Mo Kα 
µ (mm^{−}^{1})  28.37 
Crystal size (mm)  0.07 × 0.05 × 0.04 
Data collection  
Diffractometer  MAC Science M06XHF22 fourcircle diffractometer 
Absorption correction  Numerical (CCDABS; Zhurov & Tanaka, 2003) 
T_{min}, T_{max}  0.358, 0.521 
No. of measured, independent and observed [F > 3σ(F)] reflections  1255, 966, 679 
R_{int}  0.022 
(sin θ/λ)_{max} (Å^{−}^{1})  1.357 
Refinement  
R[F^{2} > 2σ(F^{2})], wR(F^{2}), S  0.028, 0.066, 1.19 
No. of reflections  927 
No. of parameters  65 
No. of restraints  14 
Δρ_{max}, Δρ_{min} (e Å^{−}^{3})  2.17, −3.38 
Computer programs: MXCSYS (MAC Science, 1995) and IUANGLE (Tanaka et al., 1994)., RSLC3 UNICS system (Sakurai & Kobayashi, 1979), RDEDIT (Tanaka, 2008), QNTAO (Tanaka & Onuki, 2002; Tanaka et al., 2008), ATOMS for Windows (Dowty, 2000).
Mn—O1  1.9199 (6)  Nd^{ii}—O2  2.545 (2) 
Mn—O2  1.9400 (4)  Nd^{i}—O1  2.7332 (5) 
Nd^{i}—O1^{i}  2.501 (4)  Nd^{ii}—O1  2.978 (4) 
Symmetry codes: (i) −x+1/2, y+1/2, z; (ii) x+1, y, z. 
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Woodward et al. (1998) and Caignaert et al. (1998) determined the structure of Nd_{0.5}Sr_{0.5}MnO_{3} on the basis of powder Xray diffraction data, whereas Kajimoto (1999) and Angappane et al. (2004) used singlecrystal Xray diffraction data for structure refinements. Except the model reported by Woodward et al. (1998), for all other structure models of Nd_{0.5}Sr_{0.5}MnO_{3} the xcoordinate of oxygen atom O1 was reported to be > 1/2. Since a new examination of the xcoordinate of O1 seemed desirable and anisotropic displacement factors were not reported in the previous studies, we decided to redetermine the structure of Nd_{0.45}Sr_{0.55}MnO_{3}. The result of the structure analysis is presented in this communication.
The structure of the title compound derives from the perovskitetype (Fig. 1) and exhibits an orthorhombic distortion. The site symmetries are 2mm for the statistically occupied [(Nd,Sr)O_{12}] polyhedron and for O1, .2/m. for the distorted [MnO_{6}] octahedron and ..2 for O2.