inorganic compounds Acta Crystallographica Section E Experimental Structure Reports Crystal data Online ˚ 3 CaCu(AsO4)(OH) V = 395.49 (2) A ISSN 1600-5368 Mr = 259.57 Z =4 Orthorhombic, P212121 Mo K radiation a = 7.3822 (2) A˚ = 15.03 mmÀ1 Redetermination of conichalcite, b = 5.8146 (2) A˚ T = 293 (2) K c = 9.2136 (3) A˚ 0.06 Â 0.05 Â 0.04 mm CaCu(AsO4)(OH) Data collection Rachel R. Henderson, Hexiong Yang,* Robert T. Downs Bruker APEXII CCD 7088 measured reflections diffractometer 1602 independent reflections and Robert A. Jenkins Absorption correction: multi-scan 1487 reflections with I >2(I) (TWINABS; Sheldrick, 2008) Rint = 0.023 Department of Geosciences, University of Arizona, 1040 E. 4th Street, Tucson, AZ Tmin = 0.492, Tmax = 0.585 85721-0077, USA (expected range = 0.461–0.548) Correspondence e-mail: [email protected] Refinement Received 2 July 2008; accepted 29 July 2008 2 2 ˚ À3 R[F >2(F )] = 0.018 Ámax = 0.63 e A wR(F 2) = 0.038 Á = À0.49 e A˚ À3 ˚ min Key indicators: single-crystal X-ray study; T = 293 K; mean (As–O) = 0.002 A; S = 1.03 Absolute structure: Flack (1983), R factor = 0.018; wR factor = 0.038; data-to-parameter ratio = 20.3. 1602 reflections 644 Friedel pairs 79 parameters Flack parameter: 0.00 (2) All H-atom parameters refined The crystal structure of conichalcite [calcium copper(II) arsenate(V) hydroxide], with ideal formula CaCu(AsO4)- (OH), was redetermined from a natural twinned specimen Table 1 ˚ found in the Maria Catalina mine (Chile). In contrast to the Selected bond lengths (A). previous refinement from photographic data [Qurashi & Ca—O5i 2.3626 (13) Cu—O5vi 1.8855 (16) Ca—O3ii 2.3995 (17) Cu—O1vi 2.0666 (16) Barnes (1963). Can. Mineral. 7, 561–577], all atoms were Ca—O4iii 2.4818 (16) Cu—O1 2.0688 (15) refined with anisotropic displacement parameters and with the Ca—O2iv 2.5178 (17) Cu—O3vii 2.2976 (15) H atom located. Conichalcite belongs to the adelite mineral Ca—O4v 2.5281 (16) Cu—O4viii 2.3882 (14) Ca—O1iv 2.5462 (14) As—O4 1.6749 (16) group. The Jahn–Teller-distorted [CuO6] octahedra share Ca—O3 2.5786 (17) As—O3 1.6779 (16) edges, forming chains running parallel to [010]. These chains Ca—O2 2.6264 (17) As—O2 1.6796 (16) are cross-linked by eight-coordinate Ca atoms and by sharing Cu—O5 1.8850 (15) As—O1 1.7099 (13) 1 1 1 3 Symmetry codes: (i) Àx þ 2; Ày þ 1; z À 2; (ii) x þ 2; Ày þ 2; Àz; (iii) x; y þ 1; z; (iv) vertices with isolated AsO4 tetrahedra. Of five calcium 1 1 1 1 1 1 Àx þ 1; y þ 2; Àz þ 2; (v) x þ 2; Ày þ 2; Àz; (vi) Àx; y À 2; Àz þ 2; (vii) 1 1 1 1 arsenate minerals in the adelite group, the [MO6](M = Cu, x À 2; Ày þ 2; Àz; (viii) Àx þ 2; Ày; z þ 2. Zn, Co, Ni and Mg) octahedron in conichalcite is the most distorted, and the donor–acceptor O—HÁÁÁO distance is the shortest. Table 2 Hydrogen-bond geometry (A˚ , ). Related literature D—HÁÁÁAD—H HÁÁÁADÁÁÁAD—HÁÁÁA For background on the adelite mineral family, see: Qurashi & O5—H1ÁÁÁO2ix 0.86 (4) 1.91 (4) 2.678 (2) 149 (3) Barnes (1963, 1964); Qurashi et al. (1953). For structure refinements in the adelite group, see: Effenberger et al. (2002) Symmetry code: (ix) x À 1; y; z. for adelite, CaMgAsO (OH); Clark et al. (1997) and Giusep- 4 Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT petti & Tadini (1988) for austinite, CaZnAsO (OH); Yang et 4 (Bruker, 2005); data reduction: SAINT; program(s) used to solve al. (2007) for cobaltaustinite, CaCoAsO4(OH); Cesbron et al. structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine (1987) for nickelaustinite, CaNiAsO4(OH). Correlations structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Xtal- between O—H streching frequencies and O—HÁÁÁO donor– Draw (Downs & Hall-Wallace, 2003); software used to prepare acceptor distances are given by Libowitzky (1999). Raman material for publication: SHELXTL (Sheldrick, 2008). spectroscopic data on some minerals of the adelite group have been reported by Martens et al. (2003); for general back- The authors gratefully acknowledge support of this study by ground, see: Robinson et al. (1971). the RRUFF project. Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2185). Acta Cryst. (2008). E64, i53–i54 doi:10.1107/S1600536808024173 Henderson et al. i53 inorganic compounds References Giuseppetti, G. & Tadini, C. (1988). Neues Jahrb. Mineral. Monatsh. 1988, 159– 166. Bruker (2003). SMART. Bruker AXS Inc., Madison, Wisconsin, USA. Libowitzky, E. (1999). Monatsh. Chem. 130, 1047–1059. Bruker (2005). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Martens, W., Frost, R. L. & Williams, P. A. (2003). J. Raman Spectrosc. 34, 104– Cesbron, F., Ginderow, D., Giraud, R., Pelisson, P. & Pillard, F. (1987). Can. 111. Mineral. 25, 401–407. Qurashi, M. M. & Barnes, W. H. (1963). Can. Mineral. 7, 561–577. Clark, L. A., Pluth, J. J., Steele, I., Smith, J. V. & Sutton, S. R. (1997). Mineral. Qurashi, M. M. & Barnes, W. H. (1964). Can. Mineral. 8, 23–39. Mag. 61, 677–683. Qurashi, M. M., Barnes, W. H. & Berry, L. G. (1953). Am. Mineral. 38, 557–559. Downs, R. T. & Hall-Wallace, M. (2003). Am. Mineral. 88, 247–250. Robinson, K., Gibbs, G. V. & Ribbe, P. H. (1971). Science, 172, 567–570. Effenberger, H., Krause, W. & Bernhardt, H. J. (2002). Exp. Miner. Petrol. Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Geochem. Abstr. 9, 30. Yang, H., Costin, G., Keogh, J., Lu, R. & Downs, R. T. (2007). Acta Cryst. E63, Flack, H. D. (1983). Acta Cryst. A39, 876–881. i53–i55. i54 Henderson et al. CaCu(AsO4)(OH) Acta Cryst. (2008). E64, i53–i54 supporting information supporting information Acta Cryst. (2008). E64, i53–i54 [doi:10.1107/S1600536808024173] Redetermination of conichalcite, CaCu(AsO4)(OH) Rachel R. Henderson, Hexiong Yang, Robert T. Downs and Robert A. Jenkins S1. Comment Minerals of the adelite group crystallize with orthorhombic symmetry in space group P212121 (Qurashi & Barnes, 1963, +,2+ 2+,3+ 4+,5+,6+ 1964) and have a general chemical formula A M (X O4)(OH), where A = Na, Ca, Pb, M = Al, Mg, Zn, Mn, Fe, Co, Cu, Ni, and X = Si, P, V, As. There are five calcium arsenates in this group: adelite CaMgAsO4(OH), austinite CaZnAsO4(OH), conichalcite CaCuAsO4(OH), nickelaustinite CaNiAsO4(OH), and cobaltaustinite, CaCoAsO4(OH). All structures of these calcium arsenate minerals have been determined previously (Qurashi & Barnes, 1963; Cesbron et al., 1987; Giuseppetti & Tadini, 1988; Clark et al., 1997; Effenberger et al., 2002; Yang et al., 2007). However, in our efforts to understand the relationships between the hydrogen bonding schemes and Raman spectra of hydrous minerals, we noted that the structural information of conichalcite needs to be improved, because this structure was refined by Qurashi & Barnes (1963) with X-ray intensity data collected by Qurashi et al. (1953) from precession photographs without anisotropic displacement parameters and localisation of the H atom position. Conichalcite can be compared with the other Ca-arsenate minerals in the adelite group. The distorted [CuO6] octahedra (i.e. elongated tetragonal bipyramids) share edges to form chains running parallel to [010], which are cross-linked by Ca atoms and by sharing vertices with isolated AsO4 tetrahedra (Fig. 1). The principal difference among the five calcium arsenates in the group is manifested in the bonding environments around the octahedrally coordinated M cations. The average M—O bond lengths appear to decrease from <Zn—O> (= 2.106 Å) in austinite (Clark et al., 1997), to <Cu—O> (= 2.099 Å) in conichalcite, <Co—O> (= 2.092 Å) in cobaltaustinite (Yang et al., 2007), <Ni—O> (= 2.085 Å) in nickelaustinite (Cesbron et al., 1987), and to <Mg—O> (= 2.075 Å) in adelite (Effenberger et al., 2002). Of these [MO6] octahedra, the Cu-octahedron, due to its strong Jahn-Teller effect, displays the greatest distortion in terms of the tetragonal elongation and angle variance (Robinson et al., 1971), which are 1.0229 and 23.58, respectively. The donor-acceptor O5—H···O2 distance in conichalcite is 2.678 (2) Å, which is the shortest of all five Ca-arsenates in the adelite group [2.723 (2) Å in austinite (Clark et al., 1997), 2.721 (7) Å in cobaltaustinite (Yang et al., 2007), 2.73 (1) Å in nickelaustinite (Cesbron et al., 1987), and 2.766 (2) Å in adelite (Effenberger et al., 2002)]. As the O—H stretching frequencies (νOH) increase with the O—H···O distance (Libowitzky,1999), we should expect the smallest νOH value for conichalcite and the largest for adelite among the five calcium arsenates in the adelite group. Indeed, the major νOH band positions determined from Raman spectra for conichalcite and adelite are, respectively, 3158 and 3550 cm-1 from Martens -1 et al. (2003), or 3161 and 3423 cm from the RRUFF project (http://rruff.info), with intermediate νOH values for the other three minerals (austinite, cobaltaustinite, and nickelaustinite). S2. Experimental The conichalcite crystal used in this study is from Maria Catalina mine, Pampa Larga Mining District, Tierra Amarilla, Chile, and is a sample from the RRUFF project (deposition No. R070430; http//rruff.info). The chemical composition, Ca(Cu0.99Zn0.01)(AsO4)(OH), was determined with a CAMECA SX50 electron microprobe (http//rruff.info). Acta Cryst.