Redetermination of conichalcite, CaCu(AsO(4))(OH).

The crystal structure of conichalcite [calcium copper(II) arsenate(V) hydroxide], with ideal formula CaCu(AsO(4))(OH), was redetermined from a natural twinned specimen found in the Maria Catalina mine (Chile). In contrast to the previous refinement from photographic data [Qurashi & Barnes (1963 ▶). Can. Mineral. 7, 561-577], all atoms were refined with anisotropic displacement parameters and with the H atom located. Conichalcite belongs to the adelite mineral group. The Jahn-Teller-distorted [CuO(6)] octa-hedra share edges, forming chains running parallel to [010]. These chains are cross-linked by eight-coordinate Ca atoms and by sharing vertices with isolated AsO(4) tetra-hedra. Of five calcium arsenate minerals in the adelite group, the [MO(6)] (M = Cu, Zn, Co, Ni and Mg) octa-hedron in conichalcite is the most distorted, and the donor-acceptor O-H⋯O distance is the shortest.

Related literature

For background on the adelite mineral family, see: Qurashi & Barnes (1963 ▶, 1964 ▶); Qurashi et al. (1953 ▶). For structure refinements in the adelite group, see: Effenberger et al. (2002 ▶) for adelite, CaMgAsO4(OH); Clark et al. (1997 ▶) and Giuseppetti & Tadini (1988 ▶) for austinite, CaZnAsO4(OH); Yang et al. (2007 ▶) for cobaltaustinite, CaCoAsO4(OH); Cesbron et al. (1987 ▶) for nickelaustinite, CaNiAsO4(OH). Correlations between O—H streching frequencies and O—H⋯O donor–acceptor distances are given by Libowitzky (1999 ▶). Raman spectroscopic data on some minerals of the adelite group have been reported by Martens et al. (2003 ▶); for general background, see: Robinson et al. (1971 ▶).

Experimental

Crystal data

CaCu(AsO4)(OH)

M = 259.57

Orthorhombic,

a = 7.3822 (2) Å

b = 5.8146 (2) Å

c = 9.2136 (3) Å

V = 395.49 (2) Å3

Z = 4

Mo Kα radiation

μ = 15.03 mm−1

T = 293 (2) K

0.06 × 0.05 × 0.04 mm

Data collection

Bruker APEXII CCD diffractometer

Absorption correction: multi-scan (TWINABS; Sheldrick, 2008 ▶) T min = 0.492, T max = 0.585 (expected range = 0.461–0.548)

7088 measured reflections

1602 independent reflections

1487 reflections with I > 2σ(I)

R int = 0.023

Refinement

R[F 2 > 2σ(F 2)] = 0.018

wR(F 2) = 0.038

S = 1.03

1602 reflections

79 parameters

All H-atom parameters refined

Δρmax = 0.63 e Å−3

Δρmin = −0.49 e Å−3

Absolute structure: Flack (1983 ▶), 644 Friedel pairs

Flack parameter: 0.00 (2)

Data collection: APEX2 (Bruker, 2003 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XtalDraw (Downs & Hall-Wallace, 2003 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808024173/wm2185sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808024173/wm2185Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

CaCu(AsO4)(OH)	F000 = 492
Mr = 259.57	Dx = 4.359 Mg m−3
Orthorhombic, P212121	Mo Kα radiation λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 3371 reflections
a = 7.3822 (2) Å	θ = 3.6–34.0º
b = 5.8146 (2) Å	µ = 15.03 mm−1
c = 9.2136 (3) Å	T = 293 (2) K
V = 395.49 (2) Å3	Euhedral, equant, green
Z = 4	0.06 × 0.05 × 0.04 mm

Bruker APEX2 CCD diffractometer	1602 independent reflections
Radiation source: fine-focus sealed tube	1487 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.023
T = 293(2) K	θmax = 34.0º
φ and ω scans	θmin = 3.5º
Absorption correction: multi-scan(TWINABS; Sheldrick, 2008)	h = −9→11
Tmin = 0.492, Tmax = 0.585	k = −9→9
7088 measured reflections	l = −14→14

Refinement on F2	All H-atom parameters refined
Least-squares matrix: full	w = 1/[σ2(Fo2) + (0.0151P)2 + 0.1227P] where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.018	(Δ/σ)max < 0.001
wR(F2) = 0.038	Δρmax = 0.63 e Å−3
S = 1.03	Δρmin = −0.49 e Å−3
1602 reflections	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
79 parameters	Extinction coefficient: 0.0029 (5)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), 644 Friedel pairs
Secondary atom site location: difference Fourier map	Flack parameter: 0.00 (2)
Hydrogen site location: difference Fourier map

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 > σ(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
Ca	0.61727 (5)	0.72961 (8)	0.07340 (4)	0.01133 (12)
Cu	−0.00416 (4)	−0.00002 (6)	0.25029 (4)	0.00898 (8)
As	0.36728 (2)	0.26438 (4)	0.08118 (2)	0.00768 (6)
O1	0.18844 (17)	0.2450 (3)	0.19847 (15)	0.0135 (3)
O2	0.5395 (2)	0.3313 (3)	0.19256 (18)	0.0187 (4)
O3	0.3514 (2)	0.4927 (3)	−0.02947 (17)	0.0157 (3)
O4	0.3885 (2)	0.0147 (3)	−0.00782 (15)	0.0145 (4)
O5	−0.13880 (18)	0.2539 (3)	0.31777 (14)	0.0113 (3)
H1	−0.229 (5)	0.232 (6)	0.260 (3)	0.055 (11)*

	U11	U22	U33	U12	U13	U23
Ca	0.01169 (18)	0.0119 (2)	0.01041 (18)	−0.00064 (17)	−0.00072 (13)	0.00020 (18)
Cu	0.00885 (11)	0.00621 (12)	0.01190 (12)	0.00029 (9)	0.00211 (8)	−0.00121 (8)
As	0.00801 (8)	0.00659 (9)	0.00845 (9)	0.00006 (8)	0.00059 (7)	0.00014 (9)
O1	0.0141 (6)	0.0107 (7)	0.0157 (6)	−0.0025 (7)	0.0035 (5)	−0.0006 (7)
O2	0.0146 (7)	0.0212 (9)	0.0205 (8)	−0.0029 (6)	−0.0048 (6)	0.0004 (7)
O3	0.0201 (7)	0.0107 (7)	0.0164 (7)	0.0011 (7)	0.0044 (7)	0.0035 (6)
O4	0.0181 (8)	0.0096 (7)	0.0158 (8)	0.0018 (6)	0.0022 (7)	−0.0018 (6)
O5	0.0106 (5)	0.0102 (6)	0.0132 (6)	0.0000 (8)	0.0002 (5)	−0.0003 (6)

Ca—O5i	2.3626 (13)	Cu—O5vi	1.8855 (16)
Ca—O3ii	2.3995 (17)	Cu—O1vi	2.0666 (16)
Ca—O4iii	2.4818 (16)	Cu—O1	2.0688 (15)
Ca—O2iv	2.5178 (17)	Cu—O3vii	2.2976 (15)
Ca—O4v	2.5281 (16)	Cu—O4viii	2.3882 (14)
Ca—O1iv	2.5462 (14)	As—O4	1.6749 (16)
Ca—O3	2.5786 (17)	As—O3	1.6779 (16)
Ca—O2	2.6264 (17)	As—O2	1.6796 (16)
Cu—O5	1.8850 (15)	As—O1	1.7099 (13)
O5i—Ca—O3ii	75.88 (5)	O4v—Ca—O2	77.15 (5)
O5i—Ca—O4iii	73.62 (5)	O1iv—Ca—O2	79.00 (5)
O3ii—Ca—O4iii	89.42 (5)	O3—Ca—O2	61.06 (5)
O5i—Ca—O2iv	151.07 (5)	O5—Cu—O5vi	177.68 (6)
O3ii—Ca—O2iv	108.51 (6)	O5—Cu—O1vi	98.01 (6)
O4iii—Ca—O2iv	77.79 (5)	O5vi—Cu—O1vi	84.26 (6)
O5i—Ca—O4v	74.41 (5)	O5—Cu—O1	84.21 (6)
O3ii—Ca—O4v	76.55 (5)	O5vi—Cu—O1	93.52 (6)
O4iii—Ca—O4v	147.36 (3)	O1vi—Cu—O1	177.66 (7)
O2iv—Ca—O4v	134.48 (5)	O5—Cu—O3vii	91.88 (6)
O5i—Ca—O1iv	141.59 (5)	O5vi—Cu—O3vii	88.82 (6)
O3ii—Ca—O1iv	73.13 (5)	O1vi—Cu—O3vii	84.84 (6)
O4iii—Ca—O1iv	127.50 (5)	O1—Cu—O3vii	95.85 (6)
O2iv—Ca—O1iv	62.85 (5)	O5—Cu—O4viii	84.76 (6)
O4v—Ca—O1iv	76.76 (5)	O5vi—Cu—O4viii	94.77 (6)
O5i—Ca—O3	72.94 (5)	O1vi—Cu—O4viii	89.81 (6)
O3ii—Ca—O3	147.75 (2)	O1—Cu—O4viii	89.67 (5)
O4iii—Ca—O3	74.21 (5)	O3vii—Cu—O4viii	173.23 (6)
O2iv—Ca—O3	95.19 (5)	O4—As—O3	113.27 (7)
O4v—Ca—O3	102.41 (5)	O4—As—O2	115.43 (8)
O1iv—Ca—O3	138.68 (5)	O3—As—O2	103.94 (8)
O5i—Ca—O2	117.86 (6)	O4—As—O1	108.94 (8)
O3ii—Ca—O2	145.22 (5)	O3—As—O1	112.45 (8)
O4iii—Ca—O2	124.48 (5)	O2—As—O1	102.33 (7)
O2iv—Ca—O2	75.44 (3)

D—H···A	D—H	H···A	D···A	D—H···A
O5—H1···O2ix	0.86 (4)	1.91 (4)	2.678 (2)	149 (3)

Table 1

Selected bond lengths (Å)

Ca—O5i	2.3626 (13)
Ca—O3ii	2.3995 (17)
Ca—O4iii	2.4818 (16)
Ca—O2iv	2.5178 (17)
Ca—O4v	2.5281 (16)
Ca—O1iv	2.5462 (14)
Ca—O3	2.5786 (17)
Ca—O2	2.6264 (17)
Cu—O5	1.8850 (15)
Cu—O5vi	1.8855 (16)
Cu—O1vi	2.0666 (16)
Cu—O1	2.0688 (15)
Cu—O3vii	2.2976 (15)
Cu—O4viii	2.3882 (14)
As—O4	1.6749 (16)
As—O3	1.6779 (16)
As—O2	1.6796 (16)
As—O1	1.7099 (13)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) .

Table 2

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O5—H1⋯O2ix	0.86 (4)	1.91 (4)	2.678 (2)	149 (3)

Symmetry code: (ix) .