Acta Cryst. (2007). E63, i160 [ doi:10.1107/S1600536807028942 ]
Single crystals of disodium beryllodiborate have been obtained by spontaneous nucleation from a high-temperature melt. Na2[BeB2O5] adopts a new structure type and contains [BeB2O7]6- rings as building units that are made up from one BeO4 tetrahedron and two BO3 triangles. These rings are further condensed and form {[BeB2O5]2-}![[infinity]](http://journals.iucr.org/logos/entities/infin_rmgif.gif)
two-dimensional layers extending parallel to the ab plane with the Na+ cations in a [6 + 1] coordination located between the layers. All atoms except Be and an O atom (both with site symmetry .2) are in general positions.
Single crystals of compound (I) were grown using a Na4B2O5 flux. The composition of the mixture for crystal growth was 2:1:3 of Na2CO3 (Hongguang Materials, 99.8%), BeO (Shuikoushan Materials, 99.8%), and H3BO3 (Jinghua Materials, 95%). This mixture was heated in a Pt crucible to 1073 K, held at this temperature for several hours, and then cooled at a rate of 3 K h−1 from 1073 to 873 K. The remaining solified flux attached to the crystals was readily dissolved in water. Crystals with an average size of 0.5 mm and mostly block-shaped habit were obtained.
Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2004); software used to prepare material for publication: enCIFer (Allen et al., 2004).
![[Figure 1]](./wm2126fig1thm.gif)
| Fig. 1. The structure of (I) in a projection approximately along the a axis with anisotropic displacement ellispoids drawn at the 60% probability level. Na—O bonds were omitted for clarity. |
![[Figure 2]](./wm2126fig2thm.gif)
| Fig. 2. [BeB2O7](6-) building unit in compound (I). |
| Na2[BeB2O5] | F000 = 304 |
| Mr = 156.61 | Dx = 2.475 Mg m−3 |
| Monoclinic, C2/c | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: -C 2yc | Cell parameters from 616 reflections |
| a = 5.8117 (5) Å | θ = 2.3–27.5º |
| b = 8.1666 (7) Å | µ = 0.39 mm−1 |
| c = 8.9830 (8) Å | T = 293 (2) K |
| β = 99.665 (14)º | Prism, colourless |
| V = 420.30 (7) Å3 | 0.12 × 0.10 × 0.05 mm |
| Z = 4 |
| Rigaku Mercury CCD diffractometer | 489 independent reflections |
| Radiation source: Sealed Tube | 450 reflections with I > 2σ(I) |
| Monochromator: Graphite Monochromator | Rint = 0.014 |
| Detector resolution: 14.6306 pixels mm-1 | θmax = 27.5º |
| T = 293.1500 K | θmin = 4.4º |
| CCD_Profile_fitting scans | h = −7→7 |
| Absorption correction: multi-scan (CrystalClear; Rigaku, 2000) | k = −9→10 |
| Tmin = 0.866, Tmax = 0.884 | l = −10→11 |
| 1621 measured reflections |
| Refinement on F2 | Primary atom site location: structure-invariant direct methods |
| Least-squares matrix: full | Secondary atom site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.022 | w = 1/[σ2(Fo2) + (0.0287P)2 + 0.2765P] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.059 | (Δ/σ)max < 0.001 |
| S = 1.17 | Δρmax = 0.22 e Å−3 |
| 489 reflections | Δρmin = −0.18 e Å−3 |
| 48 parameters | Extinction correction: none |
| Na2[BeB2O5] | V = 420.30 (7) Å3 |
| Mr = 156.61 | Z = 4 |
| Monoclinic, C2/c | Mo Kα |
| a = 5.8117 (5) Å | µ = 0.39 mm−1 |
| b = 8.1666 (7) Å | T = 293 (2) K |
| c = 8.9830 (8) Å | 0.12 × 0.10 × 0.05 mm |
| β = 99.665 (14)º |
| Rigaku Mercury CCD diffractometer | 489 independent reflections |
| Absorption correction: multi-scan (CrystalClear; Rigaku, 2000) | 450 reflections with I > 2σ(I) |
| Tmin = 0.866, Tmax = 0.884 | Rint = 0.014 |
| 1621 measured reflections |
| R[F2 > 2σ(F2)] = 0.022 | 48 parameters |
| wR(F2) = 0.059 | Δρmax = 0.22 e Å−3 |
| S = 1.17 | Δρmin = −0.18 e Å−3 |
| 489 reflections |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R– factors based on ALL data will be even larger. |
| x | y | z | Uiso*/Ueq | ||
| Na | −0.01389 (8) | 0.30641 (6) | 0.42612 (6) | 0.0142 (2) | |
| O1 | −0.34432 (14) | 0.32884 (10) | 0.15850 (10) | 0.0113 (2) | |
| O2 | 0.16865 (14) | 0.58926 (10) | 0.37065 (10) | 0.0108 (2) | |
| O3 | 0 | 0.07376 (14) | 0.25 | 0.0140 (3) | |
| B | −0.3344 (2) | 0.49318 (16) | 0.17748 (15) | 0.0087 (3) | |
| Be | −0.5 | 0.2100 (2) | 0.25 | 0.0087 (4) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Na | 0.0145 (3) | 0.0145 (3) | 0.0150 (3) | −0.00079 (18) | 0.0065 (2) | −0.00110 (18) |
| O1 | 0.0127 (4) | 0.0078 (4) | 0.0154 (4) | −0.0005 (3) | 0.0082 (3) | −0.0002 (3) |
| O2 | 0.0109 (4) | 0.0099 (4) | 0.0124 (4) | 0.0028 (3) | 0.0046 (3) | 0.0008 (3) |
| O3 | 0.0135 (6) | 0.0073 (6) | 0.0243 (7) | 0 | 0.0120 (5) | 0 |
| B | 0.0074 (6) | 0.0097 (6) | 0.0087 (6) | 0.0003 (4) | 0.0008 (5) | 0.0010 (5) |
| Be | 0.0090 (9) | 0.0064 (9) | 0.0115 (10) | 0 | 0.0043 (8) | 0 |
| Na—O2i | 2.3279 (10) | O2—Nai | 2.3279 (10) |
| Na—O1ii | 2.3402 (9) | O2—Naviii | 2.5473 (9) |
| Na—O1iii | 2.4203 (10) | O3—Bv | 1.4123 (14) |
| Na—O3 | 2.4824 (10) | O3—Bix | 1.4123 (14) |
| Na—O2iv | 2.5473 (9) | O3—Naii | 2.4824 (10) |
| Na—O2 | 2.6243 (9) | B—O1 | 1.3529 (15) |
| Na—Bv | 2.8128 (14) | B—O2ii | 1.3675 (15) |
| Na—Bii | 2.8145 (14) | B—O3x | 1.4123 (14) |
| Na—O1 | 2.8197 (10) | B—Naxi | 2.8128 (14) |
| Na—Bevi | 2.9000 (6) | B—Naii | 2.8145 (14) |
| Na—B | 3.0639 (13) | Be—O1xii | 1.6391 (14) |
| Na—Be | 3.0991 (7) | Be—O2v | 1.6584 (14) |
| O1—Be | 1.6391 (14) | Be—O2iv | 1.6584 (14) |
| O1—Naii | 2.3402 (9) | Be—Navi | 2.9000 (6) |
| O1—Navii | 2.4203 (10) | Be—Navii | 2.9000 (6) |
| O2—Bii | 1.3675 (15) | Be—Naxii | 3.0991 (7) |
| O2—Beviii | 1.6584 (14) | ||
| O2i—Na—O1ii | 135.07 (4) | Be—O1—Na | 83.58 (4) |
| O2i—Na—O1iii | 69.25 (3) | Naii—O1—Na | 75.89 (3) |
| O1ii—Na—O1iii | 93.45 (3) | Navii—O1—Na | 145.70 (4) |
| O2i—Na—O3 | 146.94 (3) | Bii—O2—Beviii | 120.32 (8) |
| O1ii—Na—O3 | 74.16 (3) | Bii—O2—Nai | 147.49 (8) |
| O1iii—Na—O3 | 98.53 (3) | Beviii—O2—Nai | 91.79 (4) |
| O2i—Na—O2iv | 92.62 (3) | Bii—O2—Naviii | 86.32 (7) |
| O1ii—Na—O2iv | 130.21 (3) | Beviii—O2—Naviii | 92.48 (6) |
| O1iii—Na—O2iv | 91.58 (3) | Nai—O2—Naviii | 87.38 (3) |
| O3—Na—O2iv | 56.11 (2) | Bii—O2—Na | 83.32 (7) |
| O2i—Na—O2 | 92.78 (3) | Beviii—O2—Na | 115.71 (6) |
| O1ii—Na—O2 | 57.28 (3) | Nai—O2—Na | 87.22 (3) |
| O1iii—Na—O2 | 116.52 (3) | Naviii—O2—Na | 151.43 (4) |
| O3—Na—O2 | 119.69 (3) | Bv—O3—Bix | 124.46 (14) |
| O2iv—Na—O2 | 151.43 (4) | Bv—O3—Na | 88.00 (6) |
| O2i—Na—O1 | 110.32 (3) | Bix—O3—Na | 138.43 (6) |
| O1ii—Na—O1 | 103.51 (3) | Bv—O3—Naii | 138.43 (6) |
| O1iii—Na—O1 | 152.30 (3) | Bix—O3—Naii | 88.00 (6) |
| O3—Na—O1 | 66.22 (2) | Na—O3—Naii | 80.12 (4) |
| O2iv—Na—O1 | 60.74 (3) | O1—B—O2ii | 123.15 (11) |
| O2—Na—O1 | 91.15 (3) | O1—B—O3x | 120.16 (11) |
| B—O1—Be | 122.68 (10) | O2ii—B—O3x | 116.70 (11) |
| B—O1—Naii | 95.57 (7) | O1—Be—O1xii | 107.35 (12) |
| Be—O1—Naii | 135.44 (7) | O1—Be—O2v | 109.86 (4) |
| B—O1—Navii | 124.34 (7) | O1xii—Be—O2v | 111.37 (4) |
| Be—O1—Navii | 89.03 (5) | O1—Be—O2iv | 111.37 (4) |
| Naii—O1—Navii | 86.55 (3) | O1xii—Be—O2iv | 109.86 (4) |
| B—O1—Na | 87.04 (7) | O2v—Be—O2iv | 107.07 (12) |
| Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x, y, −z+1/2; (iii) x+1/2, −y+1/2, z+1/2; (iv) x−1/2, y−1/2, z; (v) −x−1/2, y−1/2, −z+1/2; (vi) −x−1/2, −y+1/2, −z+1; (vii) x−1/2, −y+1/2, z−1/2; (viii) x+1/2, y+1/2, z; (ix) x+1/2, y−1/2, z; (x) x−1/2, y+1/2, z; (xi) −x−1/2, y+1/2, −z+1/2; (xii) −x−1, y, −z+1/2. |
| Na—O2i | 2.3279 (10) | Na—O1 | 2.8197 (10) |
| Na—O1ii | 2.3402 (9) | B—O1 | 1.3529 (15) |
| Na—O1iii | 2.4203 (10) | B—O2ii | 1.3675 (15) |
| Na—O3 | 2.4824 (10) | B—O3v | 1.4123 (14) |
| Na—O2iv | 2.5473 (9) | Be—O1vi | 1.6391 (14) |
| Na—O2 | 2.6243 (9) | Be—O2vii | 1.6584 (14) |
| O1—B—O2ii | 123.15 (11) | O1—Be—O2vii | 109.86 (4) |
| O1—B—O3v | 120.16 (11) | O1—Be—O2iv | 111.37 (4) |
| O2ii—B—O3v | 116.70 (11) | O2vii—Be—O2iv | 107.07 (12) |
| O1—Be—O1vi | 107.35 (12) |
| Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x, y, −z+1/2; (iii) x+1/2, −y+1/2, z+1/2; (iv) x−1/2, y−1/2, z; (v) x−1/2, y+1/2, z; (vi) −x−1, y, −z+1/2; (vii) −x−1/2, y−1/2, −z+1/2. |
This material is based upon work supported by the Science and Technology Foundation of Fujian Province under grant No. 2005H046 and the National Science Foundation of China under grant No. 60608018.
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Borate crystals containing parallell aligned BO3 anions are predicted to have large nonlinear optical (NLO) coefficients, moderate birefringence and wide transparency in the UV region. Therefore they are considered to be good candidates for NLO applications (Chen et al., 1999). Based on a theoretical study, beryllium borates possess the largest energy gap among all alkaline and alkaline earth borates, and hence the shortest transmission cut-off wavelength (Li, 1989). Therefore, beryllium borates are studied intensively with the purpose of searching for new NLO materials in the UV region. The title compound, Na2[BeB2O5], (I), was found from the investigation of the pseudo-ternary system Na2O-BeO-B2O3.
A perspective view of the structure of (I) along the a direction is shown in Fig.1. The Be atoms are bonded to four O atoms to form slightly distorted BeO4 tetrahedra (site symmetry. 2). The Be—O bonds can be classified into two groups with different bond lengths of 1.6391 (14) Å for Be—O1 and 1.6584 (14) Å for Be—O2. The O—Be—O angles vary from 107.07 (12) to 111.37 (4)°, indicating a slight distortion from the ideal tetrahedron. The B atoms are coordinated to three O atoms to form planar BO3 triangles with a mean B—O bond length of 1.378 Å (Table 1) and O—B—O angles ranging from 116.70 (11) to 123.15 (11)°, which is in good agreement with the results of geometric studies for the triangular BO3 group (Zobetz, 1982). Two BO3 groups, slightly tilted against each other, share one O3 atom, and each of them also share a different O1 atom with a BeO4 tetrahedron to form a six-membered [BeB2O7]6− ring (Fig. 2). These [BeB2O7]6− rings are further condensed, resulting in a [BeB2O5]∞2− layer parallel to the ab plane. Between adjacent [BeB2O5]∞2− layers the Na+ cations are located in a [6 + 1] coordination, with one considerably longer Na—O bond of 2.8197 (10) Å (Table 1).
The conformation of the [BeB2O7]6− rings is similar to that of the [B3O7]5− units in LiB3O5 (LBO) (Chen et al., 2005), with the BO4 tetrahedron replaced by a BeO4 tetrahedron. From the study of LBO, it is known that the [B3O7]5− group can yield large NLO effects and short UV transmission cut-offs, but the spatial arrangement of the helical [B3O5]∞ chains along the c axis is unfavorable for the generation of a large birefringence. Therefore, compounds with a [BeB2O5]∞ layer structure may be good candidates for deep UV NLO applications. Unfortunately, in the case of (I), the direction of the [BeB2O7]6− groups in the two adjacent layers are completely opposite, and thus their contributions to the NLO effect are eliminated.