New M+, M3+-arsenates - the framework structures of AgM3+(HAsO4)2 (M3+ = Al, Ga) and M+GaAs2O7 (M+ = Na, Ag).

The crystal structures of hydro-thermally synthesized silver(I) aluminium bis-[hydrogen arsenate(V)], AgAl(HAsO4)2, silver(I) gallium bis-[hydrogen arsenate(V)], AgGa(HAsO4)2, silver gallium diarsenate(V), AgGaAs2O7, and sodium gallium diarsenate(V), NaGaAs2O7, were determined from single-crystal X-ray diffraction data collected at room temperature. The first two compounds are representatives of the MCV-3 structure type known for KSc(HAsO4)2, which is characterized by a three-dimensional anionic framework of corner-sharing alternating M3+O6 octa-hedra (M = Al, Ga) and singly protonated AsO4 tetra-hedra. Inter-secting channels parallel to [101] and [110] host the Ag+ cations, which are positionally disordered in the Ga compound, but not in the Al compound. The hydrogen bonds are relatively strong, with O⋯O donor-acceptor distances of 2.6262 (17) and 2.6240 (19) Å for the Al and Ga compounds, respectively. The two diarsenate compounds are representatives of the NaAlAs2O7 structure type, characterized by an anionic framework topology built of M3+O6 octa-hedra (M = Al, Ga) sharing corners with diarsenate groups, and M+ cations (M = Ag) hosted in the voids of the framework. Both structures are characterized by a staggered conformation of the As2O7 groups.

Chemical context

Metal arsenates often form tetra­hedral–octa­hedral framework structures with potentially inter­esting properties, such as ion conductivity, ion exchange and catalytic properties (Masquelier et al., 1990 ▸, 1994a ▸,b ▸, 1995 ▸, 1996 ▸; Medvedev et al., 2003 ▸; Ouerfelli et al., 2007a ▸, 2008 ▸; Pintard-Scrépel et al., 1983 ▸; Rousse et al., 2013 ▸). A detailed study of the system M +–M 3+–As–O–(H) was therefore conducted, and a wide variety of new compounds and structure types were found and have been published (Schwendtner, 2006 ▸; Schwendtner & Kolitsch, 2004a ▸,b ▸, 2005 ▸, 2007a ▸,b ▸,c ▸,d ▸). Thus far, three different structure types for M 1+ M 3+(HAsO4)2 compounds have been reported. Two of them are very common and were first described for isotypic phosphate compounds. The (H3O)Fe(HPO4)2 type (Vencato et al., 1989 ▸) is also adopted by β-CsSc(HAsO4)2 (Schwendtner & Kolitsch, 2004b ▸), while the (NH4)Fe(HPO4)2 type (Yakubovich, 1993 ▸) is adopted by α-CsSc(HAsO4)2 (Schwendtner & Kolitsch, 2004 ▸) and (NH4)Fe(HAsO4)2 (Ouerfelli et al., 2014 ▸). The KSc(HAsO4)2 type (Schwendtner & Kolitsch, 2004a ▸) has so far been the only known example; the two new protonated arsenates presented here are two further representatives of this structure type.

M + M 3+As2O7 compounds crystallize in six known structure types, some of them isotypic to phosphates or silicates. The CaZrSi2O7 type (mineral gittinsite; Roelofsen-Ahl & Peterson, 1989 ▸) is also adopted by LiFeAs2O7 (Wang et al., 1994 ▸), LiM 3+As2O7 (M 3+ = Al, Ga, Sc) and NaScAs2O7 (Schwendtner & Kolitsch, 2007d ▸). The NaInAs2O7 type (Belam et al., 1997 ▸) has no other known members. The TlInAs2O7 type (M + = Tl, Rb, NH4) (Schwendtner, 2006 ▸) is also adopted by KFeAs2O7 (Ouerfelli et al., 2007b ▸). The RbAlAs2O7 type (Boughzala et al., 1993 ▸) is also known for M 1+ = Tl, Cs (Boughzala & Jouini, 1992 ▸), M 1+ = K (Boughzala & Jouini, 1995 ▸), and is further represented by KGaAs2O7 (Lin & Lii, 1996 ▸), KCrAs2O7 (Siegfried et al., 2004 ▸) and the mixed (Al/Fe) compound TlAl0.78Fe0.22As2O7 (Ouerfelli et al., 2007a ▸). The KAlP2O7 type is extremely common for phosphates and also has five examples that are arsenates, M +ScAs2O7 with M + = NH4 (Kolitsch, 2004 ▸), Rb (Schwendtner & Kolitsch, 2004a ▸), and Tl (Baran et al., 2006 ▸), as well as CsCrAs2O7 (Bouhassine & Boughzala, 2015 ▸), and the mixed (Al/Cr) compound K(Al0.75Cr0.25)As2O7 (Bouhassine & Boughzala, 2017 ▸). The NaAlAs2O7 type (Driss & Jouini, 1994 ▸) is also known for AgFeAs2O7 and NaFeAs2O7 (Ouerfelli et al., 2004 ▸), and the M12+ M22+ representative CaCuAs2O7 (Chen & Wang, 1996 ▸). The two diarsenates presented here also adopt the NaAlAs2O7 structure type.

Structural commentary

AgAl(HAsO4)2 and AgGa(HAsO4)2 are isotypic and crystallize in the monoclinic (C2/c) microporous framework structure of KSc(HAsO4)2 (Schwendtner & Kolitsch, 2004a ▸). The asymmetric unit contains one Ag, one Ga/Al, one As, four O and one H sites (Fig. 1 ▸). The Al/Ga atoms lie on a special position (twofold rotation axis) and the Ag+ cation is situated on an inversion centre. In the case of AgGa(HAsO4)2, the Ag+ cation occupies a split position (Fig. 1 ▸ b), where Ag1 sits on the inversion centre, with a freely refined occupancy of 0.75 (2). The second site (Ag2) is only 0.31 (3) Å away from Ag1 and has a freely refined occupancy of 0.123 (10). In total, this leads to a composition of one Ag atom per formula unit. The slightly distorted M 3+O6 octa­hedra share corners with six hydrogen arsenate tetra­hedra to form a three-dimensional, anionic framework structure with narrow irregular channels parallel to [101] and [110] (Fig. 2 ▸), which host the Ag+ cations. The latter show a rather irregular [6 + 2]-coordination in both compounds. However, it is well known that Ag atoms tolerate a broad spectrum of coordination spheres (Müller-Buschbaum, 2004 ▸).

Figure 1

The principal building units of (a) AgAl(HAsO4)2 and (b) AgGa(HAsO4)2, shown as displacement ellipsoids at the 70% probability level. The H atom is shown as a sphere with arbitrary radius. Part (b) shows the split position for Ag in AgGa(HAsO4)2. [Symmetry codes: (ii) −x, y, −z + ; (iii) x + , y + , z; (iv) −x + , y + , −z + ; (vii) −x + , −y + , −z; (viii) x + , −y + , z − .]

Figure 2

View of the framework structure of (a) AgAl(HAsO4)2 along [101] and (b) isotypic AgGa(HAsO4)2 along [110]. The M 3+O6 octa­hedra (M = Al, Ga) are corner-linked to HAsO4 tetra­hedra. Both views show small micropores in which the Ag+ cations are situated; the split Ag position (see text) and hydrogen bonds (dashed lines) are indicated in (b).

The protonated apex of the AsO4 tetra­hedron is involved in a relatively strong hydrogen bond with O4⋯O2(x, −y + 1, z + ) = 2.6212 (17) and 2.6240 (19) Å for the Al (Table 2 ▸) and Ga compounds (Table 4 ▸), respectively, which runs roughly perpendicular to the (101) plane (Fig. 2 ▸). The As—OH bond lengths (Tables 1 ▸ and 3 ▸) are considerably elongated in comparison to the three remaining As—O bonds (Ferraris & Ivaldi, 1984 ▸), but at 1.7161 (10) Å for the Al and 1.7096 (12) Å for the Ga compound are slightly shorter than the average As—OH bond length in HAsO4 2− anions of 1.72 (3) Å (Schwendtner, 2008 ▸). The bonds to non-protonated O ligands are shorter than the average mean As—O bond length for inorganic arsenates (1.686 Å; Schwendtner, 2008 ▸), and fit well with the data for As bonds to non-protonated O atoms in H1–3AsO4 groups [average 1.669 Å, Schwendtner, 2008 ▸; 1.670 Å, AgAl(HAsO4)2; 1.675 Å, AgGa(HAsO4)2]. The average bond lengths for the AlO6 and GaO6 octa­hedra agree well with published averages (Baur, 1981 ▸; Overweg et al., 1999 ▸). Bond-valence sums were calculated using the bond-valence parameters of Brown & Altermatt (1985 ▸), and amount to 0.88/0.90 (Ag1), 0.89 (Ag2), 3.05/3.16 (Al/Ga), 5.05/5.02 (As), 2.04/2.06 (O1), 1.85/1.85 (O2), 1.90/2.01 (O3) and 1.22/1.21 (O4 = OH; H atom not considered for calculation) valence units for AgAl(HAsO4)2 and AgGa(HAsO4)2, respectively. These results are reasonably close to the ideal values; the underbonded O2 is an acceptor of the strong hydrogen bond. Compared to isotypic KSc(HAsO4)2, the cell lengths and the hydrogen bonds of the two new compounds are considerably shorter. As a result of the similar ionic radii of Al3+ and Ga3+, these two compounds have similar unit-cell parameters. The Ga compound is slightly compressed along the a axis (smaller β), but elongated along the b axis; the c axis is not affected.

Table 2

Hydrogen-bond geometry (Å, °) for AgAl(HAsO4)2

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H⋯O2v	0.89 (1)	1.81 (2)	2.6212 (17)	151 (3)

Symmetry code: (v) .

Table 4

Hydrogen-bond geometry (Å, °) for AgGa(HAsO4)2

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H⋯O2viii	0.80 (3)	1.89 (3)	2.6240 (19)	153 (3)

Symmetry code: (viii) .

Table 1

Selected bond lengths (Å) for AgAl(HAsO4)2

Ag1—O1	2.4040 (11)	Al—O3iv	1.9167 (10)
Ag1—O3i	2.6362 (11)	As—O2	1.6683 (9)
Ag1—O4ii	2.8202 (13)	As—O1	1.6697 (10)
Ag1—O2	3.1259 (11)	As—O3	1.6710 (11)
Al—O1	1.8920 (10)	As—O4	1.7161 (10)
Al—O2iii	1.8955 (11)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Table 3

Selected bond lengths (Å) for AgGa(HAsO4)2

Ag1—O1	2.3600 (12)	Ag2—O2iii	3.116 (18)
Ag1—O3i	2.5864 (12)	Ag2—O2	3.185 (17)
Ag1—O4ii	3.0574 (15)	Ga—O1	1.9591 (11)
Ag1—O2	3.1352 (12)	Ga—O2vi	1.9641 (11)
Ag2—O1	2.357 (17)	Ga—O3vii	1.9799 (12)
Ag2—O1iii	2.402 (18)	As—O2	1.6719 (11)
Ag2—O3i	2.48 (2)	As—O3	1.6753 (12)
Ag2—O3iv	2.73 (3)	As—O1	1.6773 (11)
Ag2—O4v	2.83 (2)	As—O4	1.7096 (12)

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

The two diarsenates AgGaAs2O7 and NaGaAs2O7 crystallize in space group P21/c and are isotypic to NaAlAs2O7 (Driss & Jouini, 1994 ▸). The asymmetric unit contains one Ag/Na, one Ga, two As and seven O sites, all of which occupy general positions (Fig. 3 ▸). The basic building block is an As2O7 group, which is connected to the GaO6 octa­hedra by two corners. The other four free O ligands are connected to different GaO6 octa­hedra to form a three-dimensional framework structure (Fig. 4 ▸). The As2—Obridge distances [1.755 (3), 1.756 (3) Å] are nearly identical to the literature value of 1.755 Å for the average As—Obridge bond length in diarsenates (Schwendtner & Kolitsch, 2007d ▸), whereas the As1—Obridge distances [1.781 (3), 1.777 (3) Å] are further elongated. The average bond lengths of both AsO4 tetra­hedra are slightly longer than the literature value of 1.688 Å (Schwendtner & Kolitsch, 2007d ▸) for the average As—O bond length in As2O7 groups. The As—O—As angle is very close to the average value of As2O7 groups in a staggered conformation (124.2°, Schwendtner & Kolitsch, 2007d ▸) for both compounds (see Tables 5 ▸ and 6 ▸).

Figure 3

The principal building units of AgGaAs2O7 shown as displacement ellipsoids at the 70% probability level. [Symmetry codes: (ii) −x, y + , −z + ; (iii) −x, −y, −z; (iv) x, −y − , z − .]

Figure 4

View of the framework structure of AgGaAs2O7 along (a) [100] and (b) [110].

Table 5

Selected geometric parameters (Å, °) for AgGa(As2O7)

Ag—O1i	2.353 (3)	Ga—O6v	1.985 (3)
Ag—O6ii	2.361 (3)	Ga—O7i	2.015 (3)
Ag—O3	2.440 (3)	As1—O2	1.653 (3)
Ag—O7iii	2.529 (3)	As1—O1	1.668 (3)
Ag—O7iv	2.600 (3)	As1—O3	1.679 (3)
Ag—O4	2.766 (3)	As1—O4	1.781 (3)
Ga—O2v	1.939 (3)	As2—O5vi	1.655 (3)
Ga—O3	1.957 (3)	As2—O7	1.674 (3)
Ga—O1iii	1.973 (3)	As2—O6	1.675 (3)
Ga—O5	1.975 (3)	As2—O4	1.755 (3)
As2—O4—As1	124.65 (15)

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

Table 6

Selected geometric parameters (Å, °) for NaGa(As2O7)

Na—O1i	2.289 (4)	Ga—O6v	1.987 (3)
Na—O6ii	2.360 (4)	Ga—O7i	2.042 (3)
Na—O3	2.364 (4)	As1—O2	1.655 (3)
Na—O7iii	2.468 (4)	As1—O1	1.664 (3)
Na—O7iv	2.479 (4)	As1—O3	1.676 (3)
Na—O4	2.624 (4)	As1—O4	1.777 (3)
Ga—O2v	1.940 (3)	As2—O5vi	1.661 (3)
Ga—O1iii	1.952 (3)	As2—O6	1.671 (3)
Ga—O3	1.960 (3)	As2—O7	1.678 (3)
Ga—O5	1.967 (3)	As2—O4	1.756 (3)
As2—O4—As1	124.73 (19)

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

The GaO6 octa­hedra are slightly distorted and the average Ga—O bond lengths are close to the literature values (∼1.96 Å; Overweg et al., 1999 ▸). The Na+ and Ag+ cations show a strongly distorted octa­hedral coordination. The calculated bond-valence sums using the parameters of Brown & Altermatt (1985 ▸) for Ag, Ga and As, and Wood & Palenik (1999 ▸) for Na, amount to 1.06/1.00 (Ag/Na), 3.11/3.11 (Ga), 4.90/4.93 (As1), 4.96/4.93 (As2), 2.08/2.11 (O1), 1.93/1.92 (O2), 2.01/2.01 (O3), 2.08/2.10 (O4), 1.87/1.86 (O5), 2.03/1.99 (O6), and 2.03/1.99 (O7) valence units for AgGaAs2O7 and NaGaAs2O7, respectively.

Synthesis and crystallization

The compounds were grown by hydro­thermal synthesis at 493 K (7 d, autogeneous pressure, slow furnace cooling) using Teflon-lined stainless-steel autoclaves with an approximate filling volume of 2 cm3. Reagent-grade Ag2CO3, Ga2O3, α-Al2O3, Na2CO3, and H3AsO4·0.5H2O were used as starting reagents in approximate volume ratios of M +:M 3+:As of 1:1:2. The vessels were filled with distilled water to about 70% of their inner volumes, which led to final pH values of < 1 for all synthesis batches except NaGaAs2O7 (pH 1.5). The reaction products were washed thoroughly with distilled water, filtered and dried at room temperature.

The two hydrogen arsenates formed pseudo-dipyramidal colourless crystals up to 2 mm in length (yield > 95% for the Al compound with minor amounts of AgCl, explained by the reaction of Ag+ with remnants of concentrated hot HCl used for standard cleaning of the Teflon vessels before each new experiment; Fig. 5 ▸ a). The crystals of AgGa(HAsO4)2 (Fig. 5 ▸ c) were accompanied by about 20% of AgGaAs2O7 as pseudo-ortho­rhom­bic platelets (Fig. 5 ▸ d). NaGaAs2O7 crystallized as small, colourless platelets with a diamond-shaped outline (yield 100%) (Fig. 5 ▸ b).

Figure 5

SEM micrographs of hydro­thermally synthesized crystals of (a) AgAl(HAsO4)2, (b) NaGaAs2O7, (c) AgGa(HAsO4)2 and (d) AgGaAs2O7.

Measured X-ray powder diffraction diagrams of the NaGaAs2O7 and AgAl(HAsO4)2 synthesis batches were deposited at the Inter­national Centre for Diffraction Data under PDF number 57-0162 (Prem et al., 2005 ▸) for NaGaAs2O7 and 57-0161 (Prem et al., 2005 ▸) for AgAl(HAsO4)2.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 7 ▸.

Table 7

Experimental details

	AgAl(HAsO4)2	AgGa(HAsO4)2	AgGa(AsO7)	NaGa(As2O7)
Crystal data
M r	414.71	457.45	354.55	439.43
Crystal system, space group	Monoclinic, C2/c	Monoclinic, C2/c	Monoclinic, P21/c	Monoclinic, P21/c
Temperature (K)	293	293	293	293
a, b, c (Å)	7.842 (2), 9.937 (2), 8.686 (2)	7.826 (2), 10.216 (2), 8.694 (2)	6.987 (1), 8.266 (2), 9.677 (2)	7.049 (1), 8.368 (2), 9.735 (2)
β (°)	108.45 (3)	107.77 (3)	107.50 (3)	108.47 (3)
V (Å3)	642.1 (3)	661.9 (3)	533.0 (2)	544.7 (2)
Z	4	4	4	4
Radiation type	Mo Kα	Mo Kα	Mo Kα	Mo Kα
μ (mm−1)	13.51	16.96	17.55	20.58
Crystal size (mm)	0.15 × 0.08 × 0.07	0.18 × 0.10 × 0.10	0.07 × 0.07 × 0.02	0.10 × 0.08 × 0.02
Data collection
Diffractometer	Nonius KappaCCD single-crystal four-circle	Nonius KappaCCD single-crystal four-circle	Nonius KappaCCD single-crystal four-circle	Nonius KappaCCD single-crystal four-circle
Absorption correction	Multi-scan (HKL SCALEPACK; Otwinowski et al., 2003 ▸)	Multi-scan (HKL SCALEPACK; Otwinowski et al., 2003 ▸)	Multi-scan (HKL SCALEPACK; Otwinowski et al., 2003 ▸)	Multi-scan (HKL SCALEPACK; Otwinowski et al., 2003 ▸)
T min, T max	0.236, 0.451	0.150, 0.282	0.373, 0.720	0.233, 0.684
No. of measured, independent and observed [I > 2σ(I)] reflections	2751, 1408, 1354	2852, 1460, 1402	3015, 1557, 1336	3849, 1982, 1775
R int	0.011	0.012	0.023	0.022
(sin θ/λ)max (Å−1)	0.806	0.806	0.704	0.757
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.014, 0.037, 1.10	0.015, 0.037, 1.15	0.033, 0.090, 1.04	0.033, 0.089, 1.05
No. of reflections	1408	1460	1557	1982
No. of parameters	62	73	100	100
No. of restraints	1	0	0	0
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	All H-atom parameters refined	–	–
Δρmax, Δρmin (e Å−3)	0.55, −0.60	0.66, −0.50	1.54, −1.49	2.29, −2.38

Computer programs: COLLECT (Nonius, 2003 ▸), HKL DENZO and SCALEPACK (Otwinowski et al., 2003 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2016 (Sheldrick, 2015 ▸), DIAMOND (Brandenburg, 2005 ▸) and publCIF (Westrip, 2010 ▸).

For easier comparison, the atomic positions of the isotypic compounds KSc(HAsO4)2 (Schwendtner & Kolitsch, 2004 ▸) and NaAlAs2O7 (Driss & Jouini, 1994 ▸) were used for the final refinement. The O—H distance was restrained to 0.9 (2) Å for AgAl(HAsO4)2 and refined freely for AgGa(HAsO4)2.

Remaining electron densities are below 1 e Å−3 for the two hydrogen arsenates. The remaining maximum and minimum electron densities in the final difference-Fourier maps are located close to the As1 atom (0.87/0.78 Å) for NaGaAs2O7, and close to the Ag atom (0.73/0.66 Å) for AgGaAs2O7.

Crystal structure: contains datablock(s) AgAlHAsO42, AgGaHAsO42, AgGaAs2O7, NaGaAs2O7. DOI: 10.1107/S2056989017005631/pk2600sup1.cif

Structure factors: contains datablock(s) AgAlHAsO42. DOI: 10.1107/S2056989017005631/pk2600AgAlHAsO42sup2.hkl

Structure factors: contains datablock(s) AgGaHAsO42. DOI: 10.1107/S2056989017005631/pk2600AgGaHAsO42sup3.hkl

Structure factors: contains datablock(s) AgGaAs2O7. DOI: 10.1107/S2056989017005631/pk2600AgGaAs2O7sup4.hkl

Structure factors: contains datablock(s) NaGaAs2O7. DOI: 10.1107/S2056989017005631/pk2600NaGaAs2O7sup5.hkl

Click here for additional data file.

Supporting information file. DOI: 10.1107/S2056989017005631/pk2600NaGaAs2O7sup6.cml

CCDC references: 1543927, 1543926, 1543925, 1543924

Additional supporting information: crystallographic information; 3D view; checkCIF report

AgAl(HAsO4)2	F(000) = 768
Mr = 414.71	Dx = 4.290 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.842 (2) Å	Cell parameters from 1477 reflections
b = 9.937 (2) Å	θ = 2.0–35.0°
c = 8.686 (2) Å	µ = 13.51 mm−1
β = 108.45 (3)°	T = 293 K
V = 642.1 (3) Å3	Pseudo-dipyramidal glassy, colourless
Z = 4	0.15 × 0.08 × 0.07 mm

Nonius KappaCCD single-crystal four-circle diffractometer	1354 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.011
φ and ω scans	θmax = 34.9°, θmin = 3.4°
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski et al., 2003)	h = −12→12
Tmin = 0.236, Tmax = 0.451	k = −16→16
2751 measured reflections	l = −13→13
1408 independent reflections

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.014	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.037	w = 1/[σ2(Fo2) + (0.018P)2 + 0.890P] where P = (Fo2 + 2Fc2)/3
S = 1.10	(Δ/σ)max = 0.001
1408 reflections	Δρmax = 0.55 e Å−3
62 parameters	Δρmin = −0.60 e Å−3
1 restraint	Extinction correction: SHELXL2016 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0114 (3)

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

	x	y	z	Uiso*/Ueq
Ag1	0.250000	0.250000	0.000000	0.03518 (7)
Al	0.000000	0.13916 (5)	0.250000	0.00554 (9)
As	0.27443 (2)	0.40001 (2)	0.35945 (2)	0.00508 (5)
O1	0.17964 (13)	0.26607 (10)	0.24940 (12)	0.00972 (16)
O2	0.32668 (13)	0.50141 (10)	0.22800 (11)	0.00973 (16)
O3	0.44856 (12)	0.35479 (10)	0.51919 (11)	0.00870 (15)
O4	0.12010 (13)	0.48544 (12)	0.42496 (12)	0.01492 (19)
H	0.153 (4)	0.487 (3)	0.5324 (12)	0.047 (9)*

	U11	U22	U33	U12	U13	U23
Ag1	0.06317 (16)	0.02460 (10)	0.03540 (12)	−0.01037 (9)	0.04068 (11)	−0.00702 (8)
Al	0.0059 (2)	0.0053 (2)	0.0052 (2)	0.000	0.00145 (16)	0.000
As	0.00555 (6)	0.00526 (7)	0.00416 (6)	−0.00071 (3)	0.00115 (4)	0.00007 (3)
O1	0.0112 (4)	0.0086 (4)	0.0102 (4)	−0.0057 (3)	0.0045 (3)	−0.0046 (3)
O2	0.0113 (4)	0.0100 (4)	0.0069 (3)	−0.0043 (3)	0.0014 (3)	0.0027 (3)
O3	0.0087 (3)	0.0117 (4)	0.0045 (3)	0.0024 (3)	0.0004 (3)	0.0009 (3)
O4	0.0113 (4)	0.0234 (5)	0.0104 (4)	0.0070 (4)	0.0038 (3)	−0.0026 (4)

Ag1—O1i	2.4040 (11)	Al—O2vii	1.8955 (11)
Ag1—O1	2.4040 (11)	Al—O2v	1.8955 (11)
Ag1—O3ii	2.6362 (11)	Al—O3viii	1.9167 (10)
Ag1—O3iii	2.6362 (11)	Al—O3iii	1.9167 (10)
Ag1—O4iv	2.8202 (13)	As—O2	1.6683 (9)
Ag1—O4v	2.8202 (13)	As—O1	1.6697 (10)
Ag1—O2	3.1259 (11)	As—O3	1.6710 (11)
Ag1—O2i	3.1259 (11)	As—O4	1.7161 (10)
Al—O1	1.8920 (10)	O4—H	0.886 (10)
Al—O1vi	1.8920 (10)
O1—Al—O1vi	96.40 (7)	O1vi—Al—O3iii	94.10 (5)
O1—Al—O2vii	172.66 (4)	O2vii—Al—O3iii	90.59 (5)
O1vi—Al—O2vii	88.33 (5)	O2v—Al—O3iii	92.00 (5)
O1—Al—O2v	88.33 (5)	O3viii—Al—O3iii	176.41 (7)
O1vi—Al—O2v	172.66 (4)	O2—As—O1	104.53 (5)
O2vii—Al—O2v	87.54 (7)	O2—As—O3	114.68 (5)
O1—Al—O3viii	94.10 (5)	O1—As—O3	111.09 (5)
O1vi—Al—O3viii	83.49 (5)	O2—As—O4	106.25 (6)
O2vii—Al—O3viii	92.00 (5)	O1—As—O4	110.56 (5)
O2v—Al—O3viii	90.59 (5)	O3—As—O4	109.54 (5)
O1—Al—O3iii	83.49 (5)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H···O2ix	0.89 (1)	1.81 (2)	2.6212 (17)	151 (3)

AgGa(HAsO4)2	F(000) = 840
Mr = 457.45	Dx = 4.590 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.826 (2) Å	Cell parameters from 1519 reflections
b = 10.216 (2) Å	θ = 2.0–35.0°
c = 8.694 (2) Å	µ = 16.96 mm−1
β = 107.77 (3)°	T = 293 K
V = 661.9 (3) Å3	Large pseudo-dipyramidal glassy, colourless
Z = 4	0.18 × 0.10 × 0.10 mm

Nonius KappaCCD single-crystal four-circle diffractometer	1402 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.012
φ and ω scans	θmax = 35.0°, θmin = 3.4°
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski et al., 2003)	h = −12→12
Tmin = 0.150, Tmax = 0.282	k = −16→16
2852 measured reflections	l = −14→13
1460 independent reflections

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.015	All H-atom parameters refined
wR(F2) = 0.037	w = 1/[σ2(Fo2) + (0.015P)2 + 0.940P] where P = (Fo2 + 2Fc2)/3
S = 1.15	(Δ/σ)max = 0.037
1460 reflections	Δρmax = 0.66 e Å−3
73 parameters	Δρmin = −0.50 e Å−3
0 restraints	Extinction correction: SHELXL2016 (Sheldrick, 2015), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0133 (3)

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

	x	y	z	Uiso*/Ueq	Occ. (<1)
Ag1	0.250000	0.250000	0.000000	0.0335 (9)	0.75 (2)
Ag2	0.284 (3)	0.2351 (14)	0.019 (2)	0.0316 (18)	0.123 (10)
Ga	0.000000	0.13670 (2)	0.250000	0.00500 (5)
As	0.27567 (2)	0.39556 (2)	0.35733 (2)	0.00482 (5)
O1	0.18942 (15)	0.26190 (10)	0.24943 (13)	0.00983 (18)
O2	0.32045 (15)	0.49738 (11)	0.22405 (13)	0.01055 (19)
O3	0.45491 (14)	0.35629 (11)	0.51333 (13)	0.00948 (18)
O4	0.11608 (16)	0.46896 (14)	0.42534 (15)	0.0169 (2)
H	0.148 (4)	0.487 (3)	0.519 (4)	0.033 (8)*

	U11	U22	U33	U12	U13	U23
Ag1	0.051 (2)	0.0368 (14)	0.0271 (9)	−0.0173 (12)	0.0327 (12)	−0.0125 (9)
Ag2	0.049 (4)	0.0249 (16)	0.035 (3)	−0.015 (2)	0.034 (3)	−0.0064 (14)
Ga	0.00555 (9)	0.00478 (9)	0.00482 (9)	0.000	0.00182 (6)	0.000
As	0.00564 (7)	0.00525 (7)	0.00364 (7)	−0.00073 (4)	0.00153 (5)	−0.00003 (4)
O1	0.0114 (4)	0.0093 (4)	0.0101 (5)	−0.0057 (3)	0.0053 (4)	−0.0045 (3)
O2	0.0122 (4)	0.0110 (4)	0.0068 (4)	−0.0060 (3)	0.0003 (3)	0.0036 (4)
O3	0.0085 (4)	0.0135 (4)	0.0053 (4)	0.0032 (3)	0.0004 (3)	0.0011 (4)
O4	0.0116 (5)	0.0299 (6)	0.0094 (5)	0.0081 (4)	0.0035 (4)	−0.0047 (4)

Ag1—O1i	2.3600 (12)	Ag2—O2	3.185 (17)
Ag1—O1	2.3600 (12)	Ga—O1	1.9591 (11)
Ag1—O3ii	2.5864 (12)	Ga—O1vi	1.9591 (11)
Ag1—O3iii	2.5864 (12)	Ga—O2vii	1.9641 (11)
Ag1—O4iv	3.0574 (15)	Ga—O2v	1.9641 (11)
Ag1—O4v	3.0574 (15)	Ga—O3viii	1.9799 (12)
Ag1—O2	3.1352 (12)	Ga—O3iii	1.9799 (12)
Ag2—O1	2.357 (17)	As—O2	1.6719 (11)
Ag2—O1i	2.402 (18)	As—O3	1.6753 (12)
Ag2—O3ii	2.48 (2)	As—O1	1.6773 (11)
Ag2—O3iii	2.73 (3)	As—O4	1.7096 (12)
Ag2—O4v	2.83 (2)	O4—H	0.80 (3)
Ag2—O2i	3.116 (18)
O1—Ga—O1vi	98.48 (7)	O3viii—Ga—O3iii	175.86 (6)
O1—Ga—O2vii	171.19 (5)	O2—As—O3	114.16 (6)
O1vi—Ga—O2vii	87.59 (5)	O2—As—O1	104.63 (6)
O1—Ga—O2v	87.59 (5)	O3—As—O1	110.64 (6)
O1vi—Ga—O2v	171.19 (5)	O2—As—O4	107.25 (7)
O2vii—Ga—O2v	87.12 (7)	O3—As—O4	110.16 (6)
O1—Ga—O3viii	94.82 (5)	O1—As—O4	109.80 (6)
O1vi—Ga—O3viii	82.46 (5)	O2—As—O3	114.16 (6)
O2vii—Ga—O3viii	92.29 (5)	O2—As—O1	104.63 (6)
O2v—Ga—O3viii	90.71 (5)	O3—As—O1	110.64 (6)
O1—Ga—O3iii	82.46 (5)	O2—As—O4	107.25 (7)
O1vi—Ga—O3iii	94.82 (5)	O3—As—O4	110.16 (6)
O2vii—Ga—O3iii	90.71 (5)	O1—As—O4	109.80 (6)
O2v—Ga—O3iii	92.29 (5)

D—H···A	D—H	H···A	D···A	D—H···A
O4—H···O2ix	0.80 (3)	1.89 (3)	2.6240 (19)	153 (3)

AgGa(As2O7)	F(000) = 800
Mr = 439.43	Dx = 5.359 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.049 (1) Å	Cell parameters from 2105 reflections
b = 8.368 (2) Å	θ = 2.0–32.6°
c = 9.735 (2) Å	µ = 20.58 mm−1
β = 108.47 (3)°	T = 293 K
V = 544.7 (2) Å3	Pseudo-orthorhombic platelets, colourless
Z = 4	0.10 × 0.08 × 0.02 mm

Nonius KappaCCD single-crystal four-circle diffractometer	1775 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.022
φ and ω scans	θmax = 32.5°, θmin = 3.1°
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski et al., 2003)	h = −10→10
Tmin = 0.233, Tmax = 0.684	k = −12→12
3849 measured reflections	l = −14→14
1982 independent reflections

Refinement on F2	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.033	Secondary atom site location: difference Fourier map
wR(F2) = 0.089	w = 1/[σ2(Fo2) + (0.0619P)2 + 0.6339P] where P = (Fo2 + 2Fc2)/3
S = 1.05	(Δ/σ)max < 0.001
1982 reflections	Δρmax = 2.29 e Å−3
100 parameters	Δρmin = −2.38 e Å−3

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

	x	y	z	Uiso*/Ueq
Ag	0.81152 (5)	0.13552 (4)	0.47918 (4)	0.02028 (11)
Ga	0.28442 (6)	0.28038 (5)	0.49133 (4)	0.00810 (11)
As1	0.52020 (5)	0.41622 (4)	0.28916 (4)	0.00783 (10)
As2	0.94310 (5)	0.54112 (4)	0.29927 (4)	0.00759 (10)
O1	0.3828 (4)	0.4083 (3)	0.1148 (3)	0.0108 (5)
O2	0.5231 (4)	0.5961 (3)	0.3601 (3)	0.0118 (5)
O3	0.4848 (4)	0.2646 (3)	0.3914 (3)	0.0107 (5)
O4	0.7697 (4)	0.3871 (3)	0.2876 (3)	0.0118 (5)
O5	0.1621 (4)	0.4491 (3)	0.3489 (3)	0.0117 (5)
O6	0.9278 (4)	0.6807 (3)	0.4187 (3)	0.0126 (5)
O7	0.8992 (4)	0.6146 (3)	0.1321 (3)	0.0113 (5)

	U11	U22	U33	U12	U13	U23
Ag	0.01549 (17)	0.01302 (15)	0.0269 (2)	−0.00362 (10)	−0.00097 (13)	0.00458 (11)
Ga	0.0088 (2)	0.00743 (18)	0.00749 (19)	0.00004 (12)	0.00177 (15)	0.00004 (12)
As1	0.00867 (19)	0.00705 (17)	0.00701 (17)	−0.00073 (11)	0.00144 (13)	−0.00004 (11)
As2	0.00788 (18)	0.00726 (17)	0.00707 (18)	0.00035 (11)	0.00158 (13)	0.00016 (11)
O1	0.0143 (13)	0.0076 (11)	0.0076 (11)	0.0007 (9)	−0.0008 (10)	0.0002 (8)
O2	0.0133 (13)	0.0080 (11)	0.0113 (12)	−0.0024 (9)	0.0002 (10)	−0.0026 (9)
O3	0.0125 (12)	0.0096 (11)	0.0114 (11)	0.0030 (9)	0.0056 (10)	0.0040 (9)
O4	0.0104 (12)	0.0080 (11)	0.0164 (13)	−0.0007 (9)	0.0033 (10)	0.0003 (9)
O5	0.0075 (11)	0.0128 (11)	0.0144 (13)	0.0043 (9)	0.0030 (10)	0.0060 (10)
O6	0.0122 (13)	0.0141 (12)	0.0120 (12)	−0.0042 (10)	0.0043 (10)	−0.0052 (10)
O7	0.0129 (13)	0.0124 (12)	0.0074 (11)	0.0015 (9)	0.0013 (10)	0.0020 (9)

Ag—O1i	2.353 (3)	Ga—O6v	1.985 (3)
Ag—O6ii	2.361 (3)	Ga—O7i	2.015 (3)
Ag—O3	2.440 (3)	As1—O2	1.653 (3)
Ag—O7iii	2.529 (3)	As1—O1	1.668 (3)
Ag—O7iv	2.600 (3)	As1—O3	1.679 (3)
Ag—O4	2.766 (3)	As1—O4	1.781 (3)
Ga—O2v	1.939 (3)	As2—O5vi	1.655 (3)
Ga—O3	1.957 (3)	As2—O7	1.674 (3)
Ga—O1iii	1.973 (3)	As2—O6	1.675 (3)
Ga—O5	1.975 (3)	As2—O4	1.755 (3)
O1i—Ag—O6ii	165.93 (10)	O3—Ga—O7i	94.90 (12)
O1i—Ag—O3	81.53 (10)	O1iii—Ga—O7i	81.24 (11)
O6ii—Ag—O3	112.42 (10)	O5—Ga—O7i	91.08 (12)
O1i—Ag—O7iii	64.14 (9)	O6v—Ga—O7i	86.83 (11)
O6ii—Ag—O7iii	106.19 (10)	O2—As1—O1	112.81 (13)
O3—Ag—O7iii	126.87 (9)	O2—As1—O3	115.14 (14)
O2v—Ga—O3	87.83 (12)	O1—As1—O3	115.19 (13)
O2v—Ga—O1iii	86.80 (11)	O2—As1—O4	104.27 (13)
O3—Ga—O1iii	94.54 (11)	O1—As1—O4	104.04 (14)
O2v—Ga—O5	100.89 (12)	O3—As1—O4	103.55 (13)
O3—Ga—O5	85.56 (11)	O5vi—As2—O7	108.84 (14)
O1iii—Ga—O5	172.30 (11)	O5vi—As2—O6	112.38 (15)
O2v—Ga—O6v	91.74 (12)	O7—As2—O6	112.71 (14)
O3—Ga—O6v	173.63 (11)	O5vi—As2—O4	104.10 (13)
O1iii—Ga—O6v	91.78 (12)	O7—As2—O4	107.22 (13)
O5—Ga—O6v	88.28 (11)	O6—As2—O4	111.12 (14)
O2v—Ga—O7i	167.90 (11)	As2—O4—As1	124.65 (15)

NaGa(AsO7)	F(000) = 656
Mr = 354.55	Dx = 4.418 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.987 (1) Å	Cell parameters from 2065 reflections
b = 8.266 (2) Å	θ = 3–30°
c = 9.677 (2) Å	µ = 17.55 mm−1
β = 107.50 (3)°	T = 293 K
V = 533.0 (2) Å3	Small platelets with diamond-shaped outline, colourless
Z = 4	0.07 × 0.07 × 0.02 mm

Nonius KappaCCD single-crystal four-circle diffractometer	1336 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.023
φ and ω scans	θmax = 30.0°, θmin = 3.1°
Absorption correction: multi-scan (HKL SCALEPACK; Otwinowski et al., 2003)	h = −9→9
Tmin = 0.373, Tmax = 0.720	k = −11→11
3015 measured reflections	l = −13→13
1557 independent reflections

Refinement on F2	100 parameters
Least-squares matrix: full	0 restraints
R[F2 > 2σ(F2)] = 0.033	w = 1/[σ2(Fo2) + (0.060P)2 + 1.1P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.090	(Δ/σ)max < 0.001
S = 1.04	Δρmax = 1.54 e Å−3
1557 reflections	Δρmin = −1.49 e Å−3

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

	x	y	z	Uiso*/Ueq
Na	0.8070 (3)	0.1389 (2)	0.4691 (2)	0.0212 (4)
Ga	0.28177 (7)	0.27455 (6)	0.49377 (5)	0.00989 (14)
As1	0.51759 (7)	0.41477 (5)	0.29095 (5)	0.00962 (13)
As2	0.94401 (7)	0.53707 (5)	0.29682 (5)	0.00931 (13)
O1	0.3798 (5)	0.4129 (4)	0.1176 (3)	0.0128 (6)
O2	0.5235 (5)	0.5967 (4)	0.3635 (4)	0.0132 (6)
O3	0.4850 (5)	0.2586 (4)	0.3921 (4)	0.0126 (6)
O4	0.7683 (5)	0.3827 (4)	0.2891 (4)	0.0137 (6)
O5	0.1637 (5)	0.4423 (4)	0.3491 (3)	0.0134 (6)
O6	0.9305 (5)	0.6834 (4)	0.4127 (4)	0.0140 (6)
O7	0.9038 (5)	0.6014 (4)	0.1260 (3)	0.0117 (6)

	U11	U22	U33	U12	U13	U23
Na	0.0190 (10)	0.0122 (9)	0.0286 (10)	−0.0006 (8)	0.0013 (8)	0.0005 (8)
Ga	0.0130 (3)	0.0074 (2)	0.0096 (2)	0.00006 (16)	0.00367 (19)	0.00009 (16)
As1	0.0125 (2)	0.0070 (2)	0.0090 (2)	−0.00080 (15)	0.00274 (17)	0.00001 (15)
As2	0.0120 (2)	0.0073 (2)	0.0086 (2)	0.00045 (15)	0.00308 (17)	0.00032 (15)
O1	0.0175 (17)	0.0087 (14)	0.0102 (14)	−0.0003 (12)	0.0011 (12)	0.0012 (12)
O2	0.0167 (16)	0.0064 (14)	0.0164 (15)	−0.0015 (11)	0.0049 (13)	−0.0028 (12)
O3	0.0166 (16)	0.0087 (14)	0.0146 (15)	0.0022 (12)	0.0080 (13)	0.0035 (12)
O4	0.0098 (15)	0.0121 (14)	0.0198 (16)	0.0002 (12)	0.0055 (12)	0.0001 (12)
O5	0.0130 (16)	0.0124 (14)	0.0142 (15)	0.0039 (12)	0.0029 (13)	0.0043 (12)
O6	0.0188 (17)	0.0120 (15)	0.0139 (14)	−0.0035 (12)	0.0088 (13)	−0.0043 (12)
O7	0.0157 (16)	0.0116 (14)	0.0082 (13)	0.0022 (12)	0.0042 (12)	0.0033 (12)

Na—O1i	2.289 (4)	Ga—O6v	1.987 (3)
Na—O6ii	2.360 (4)	Ga—O7i	2.042 (3)
Na—O3	2.364 (4)	As1—O2	1.655 (3)
Na—O7iii	2.468 (4)	As1—O1	1.664 (3)
Na—O7iv	2.479 (4)	As1—O3	1.676 (3)
Na—O4	2.624 (4)	As1—O4	1.777 (3)
Ga—O2v	1.940 (3)	As2—O5vi	1.661 (3)
Ga—O1iii	1.952 (3)	As2—O6	1.671 (3)
Ga—O3	1.960 (3)	As2—O7	1.678 (3)
Ga—O5	1.967 (3)	As2—O4	1.756 (3)
O1i—Na—O6ii	163.76 (16)	O1iii—Ga—O6v	91.80 (14)
O1i—Na—O3	80.93 (13)	O3—Ga—O6v	173.31 (13)
O6ii—Na—O3	114.82 (15)	O5—Ga—O6v	89.46 (14)
O1i—Na—O7iii	65.73 (13)	O2v—Ga—O7i	168.13 (13)
O6ii—Na—O7iii	99.98 (14)	O1iii—Ga—O7i	80.66 (14)
O3—Na—O7iii	126.13 (14)	O3—Ga—O7i	95.74 (13)
O1i—Na—O7iv	101.56 (14)	O5—Ga—O7i	91.80 (13)
O6ii—Na—O7iv	69.89 (12)	O6v—Ga—O7i	87.01 (13)
O3—Na—O7iv	137.74 (14)	O2—As1—O1	111.67 (16)
O7iii—Na—O7iv	91.40 (12)	O2—As1—O3	116.27 (16)
O1i—Na—O4	116.75 (14)	O1—As1—O3	116.25 (16)
O6ii—Na—O4	75.75 (13)	O2—As1—O4	103.93 (16)
O3—Na—O4	64.59 (11)	O1—As1—O4	105.16 (17)
O7iii—Na—O4	168.81 (15)	O3—As1—O4	101.46 (16)
O7iv—Na—O4	77.43 (12)	O5vi—As2—O6	111.76 (17)
O2v—Ga—O1iii	87.52 (13)	O5vi—As2—O7	108.37 (16)
O2v—Ga—O3	86.31 (14)	O6—As2—O7	113.90 (16)
O1iii—Ga—O3	94.67 (14)	O5vi—As2—O4	103.91 (16)
O2v—Ga—O5	100.04 (14)	O6—As2—O4	112.00 (16)
O1iii—Ga—O5	172.28 (14)	O7—As2—O4	106.27 (16)
O3—Ga—O5	84.37 (14)	As2—O4—As1	124.73 (19)
O2v—Ga—O6v	92.25 (14)