New Insight Into the Local Structure of Hydrous Ferric Arsenate Using Full-Potential Multiple Scattering Analysis, Density Functional Theory Calculations

Supporting information to

“New insight into the local structure of hydrous ferric arsenate using full-potential multiple scattering analysis, density functional theory calculations,

and vibrational spectroscopy ”

Shaofeng Wang 1, Xu Ma 1, Guoqing Zhang 1, Yongfeng Jia 1,2, *, Keisuke Hatada 3

1. Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of

Applied Ecology, Chinese Academy of Sciences, Shenyang, 110016, China

2. Institute of Environmental Protection, Shenyang University of Chemical

Technology, Shenyang, 100049, China

3. Département Matériaux Nanosciences, Institut de Physique de Rennes, UMR

UR1CNRS 6251, Université de Rennes 1, 35042 Rennes Cedex, France

* Corresponding author, Prof. Yonfeng Jia, Email: [email protected] , Tel: +86

24 83970503

This supporting information contains 9 figures, 4 tables, and references.

Contents

Figure S1 ...... 3 Figure S2 ...... 4 Figure S3 ...... 5 Figure S4 ...... 6 Figure S5 ...... 7 Figure S6 ...... 8 Figure S7...... 9 Figure S8 ...... 10 Figure S9...... 11 Table S1 ...... 12 Table S2 ...... 13 Table S3 ...... 14 Table S4 ...... 16 References ...... 21

(a) HFA

28 °

58 ° Relative instensity Relative

(b) scorodite Relative instensity Relative 10 20 30 40 50 60 70 80 2theta ( °) Figure S1 . XRD patterns of hydrous ferric arsenate (HFA)1, 2 (a) and scorodite (b).

Vertical lines in Figure S1b is the standard of scorodite (No. 370468).

Figure S2 . SEM images of synthetic HFA (left) and scorodite (right)

Figure S3. WignerSeitz cell of arsenate tetrahedron with 10 empty spheres

(a) As (b) Fe S2 = 1.5

S2 = 6.2 F11 A11 S2 = 2.3 S2 = 6.4 A10 F10 S2 = 3.9 S2 = 6.1 A9 F9 S2 = 7.7 S2 = 1.4 Normalized absorbance Normalized A8 absorbance Normalized F8

0 50 100 150 0 50 100 150 200

EE0 (eV) EE0 (eV) Figure S4 . Comparison between nonstructural optimized theoretical As (a) and Fe (b) Kedge XANES spectra (red solid lines) according to the extracted structure from scorodite (Figure 2a, b) and experimental data (black dotted lines) of HFA. For As Kedge spectra, cluster A8A11 represent As+Fe1+Fe2+Fe3, As+Fe1+Fe2+Fe4, As+Fe1+Fe3+Fe4, and As+Fe2+Fe3+Fe4, respectively. For Fe Kedge spectra, cluster F8F11 represent Fe+As1+As2+As3, Fe+As1+As2+As4, Fe+As1+As3+As4, and Fe+As2+As3+As4, respectively.

Figure S5. The butleritelike (left) and fibroferritelike (right) chain structures optimized by DFT calculations with S atoms replaced by As atoms. The unit of bond length marked in the figure is Å. The interatomic distances of FeFe in optimized butleritelike (left) and fibroferritelike (right) chain structures are ~ 3.61 and ~ 3.60 Å, respectively.

(a) butleriteAs (b) fibroferriteAs

2 2 S =10.3 S =7.9 Normalized absorbance Normalized absorbance Normalized 0 50 100 150 0 50 100 150

(c) butleriteFe (d) fibroferriteFe 2 S =2.2 S2=4.2 Normalized absorbance Normalized absorbance Normalized 0 50 100 150 200 0 50 100 150 200 EE0 (eV) EE0 (eV)

Figure S6. Comparison between theoretical and experimental data of As (a, b) and Fe

(c, d) Kedge XANES spectra based on the optimized butleritelike and fibroferritelike HFA structures proposed by Paktunc et al. 2

(a) scorodite 827 810 468 847 442 898 580 491 722 1068 Absorbance

1200 1000 800 600 400 Wavenumber (cm 1 )

812 (b) 801 scorodite 869 831 83 422 383 339 893 456 182 487 293 136 Ramanintensity 1200 1000 800 600 400 200 Wavenumber (cm 1 )

Figure S7. Deconvoluted infrared (400 – 1200 cm 1) (a) and Raman (60 – 1200 cm 1)

(b) spectra of synthetic scorodite. Black and red line represent the experimental and fitted spectra, respectively.

(a) scorodite (b) PCFA 3517 2970 3396

1623 1390 1385 1635 Absorbance Absorbance

4000 3000 2000 1000 4000 3000 2000 1000

1340 1468 1614 1345 Raman intensity Raman intensity

3000 2500 2000 1500 1000 3000 2500 2000 1500 1000 1 1 Wavenumber (cm ) Wavenumber (cm ) Figure S8. FTIR (top) and Raman (bottom) spectra of synthetic scorodite and HFA.

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835 406

865 430 492

742 923 696

985 Absorbance 939

1200 1100 1000 900 800 700 600 500 400 Wavenumber (cm 1 )

Figure S9. Comparison between experimental IR spectra and theoretical frequencies

(vertical lines) of HFA in the range of 400 – 1200 cm 1.

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Table S1 . Summary of reported values of AsFe coordination number (CN) and averaged interatomic distance in HFA

Absorber k range (Å 1) CN Distance (Å) Beamline Model Reference

As Kedge 2.714 3.2 3.33 APS scorodite 3 EXAFS 2.717.55 1.85 3.31 APS not state 4 2.716.68 1.78 3.32 CLS not state 4 5.516.6 2.7 3.32 APS not state 4 5.415.7 2.6 3.32 CLS not state 4 313 1.8 3.31 APS not state 2 317 4a 3.33 ELETTRA scorodite 5 317 2a 3.33 ELETTRA scorodite 5 Fe Kedge 2.714 3.8 3.31 APS not state 3 EXAFS 214 4a 3.34 ELETTRA scorodite 5 214 2a 3.32 ELETTRA scorodite 5 Total Xray no data no 3.32 APS no data 6 scattering data a The coordination number was fixed.

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Table S2. Interatomic distance and bond angle in the local structure shown in Figure

2 extracted from the crystalline scorodite determined by Hawthorne.7

Bond Bond length (Å) or angle (°) AsO1 1.671 Å AsO2 1.686 Å AsO3 1.681 Å AsO4 1.681 Å AsFe1 3.335 Å AsFe2 3.325 Å AsFe3 3.379 Å AsFe4 3.347 Å FeO1 1.966 Å FeO2 1.944 Å FeO3 1.960 Å FeO4 1.993 Å FeOW1 2.111 Å FeOW2 2.036 Å AsO1Fe 132.818° AsO2Fe 132.511° AsO3Fe 136.110° AsO4Fe 131.089°

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Table S3 . Fit parameters for the EXAFS data of synthetic scorodite and HFA

a b 2 2 c d 2 e f g 2 h Sample Path CN R (Å) σ (Å ) E (eV) S0 Nidp /N var R range (Å) Rfactor Reduced χ Arsenic Kedge EXAFS Scorodite AsO 4 1.69 (0) 0.003 (0) 6.6 (7) 1.0 16/9 0.93.3 0.009 100 AsFe 4 3.36 (1) 0.005 (1) AsOO 12 3.09 (5) 0.003 (6) AsOAsO 4 3.38 i 0.004i AsOFe 8 3.46 (3) 0.003 (3) HFA AsO 4 1.68 (0) 0.003 (0) 7.7 (9) 1.0 16/9 0.93.3 0.008 110 AsFe 1.5 3.30 (3) 0.009 (3) AsOO 12 3.13 (4) 0.003 (3) AsOAsO 4 3.38 i 0.004i AsOFe 3 3.47 (2) 0.002 (4) Iron Kedge EXAFS Scorodite FeO1 6 2.01 (0) 0.003 (0) 4.3 (7) 0.9 20/10 1.03.7 0.008 34 FeAs 4 3.36 (1) 0.005 (1) FeOO 24 3.51 (6) 0.006i FeOAs 8 3.48 (2) 0.003 (1) FeO2 9 3.71 (2) 0.002 (2) FeOFeO 8 4.00i 0.007i HFA FeO1 6 2.00 (2) 0.006 (1) 1.4 (8) 0.9 20/10 1.03.7 0.006 28 FeAs 1.5 3.33 (1) 0.006 (1) FeO2 4 4.09 (5) 0.007 (7) FeOAs 3 3.50 (2) 0.003 (2) FeOO 24 3.45 (7) 0.010 i

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FeOFeO 6 4.11 i 0.011 i a coordination number (degeneracy), fixed. b mean halfpath length (interatomic distance). c DebyeWaller parameter. d energyshift. e amplitude f g 2 2 h 2 reduction factor. number of independent points/number of fit variables, Rfactor = Σ i (data ifit i) /Σ i data i . reduced χ = (N idp /N pts Σi 2 2 i j (data ifit i) /ε i) )/(N idp – Nvar ), where N pts is the number of data points and ε i is the uncertainty at each data point i. Linked to the first shell. defined as ( RAsO+RAsFe )/2 . Fit uncertainties are given for the last significant figure.

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Table S4. Comparison of infrared and Raman frequencies of synthetic scorodite and HFA with theoretical frequencies of HFA and other previously reported hydrogen arsenate bearing minerals Minerals Infrared Raman Assignment HFA a 213, 271 lattice mode 2− − 424 360, 412 ν2 HAsO 4 /H 2AsO 4 symmetric bending 2− − 481 469 ν4 HAsO 4 /H 2AsO 4 antisymmetric bending 605 FeOH stretching vibrations/AsOH stretching vibrations from H2AsO 4 groups 748 766 composite of AsOH stretching vibrations from H2AsO 4 groups and AsOFe stretching 2 vibrations from HAsO 4 groups

827 825 composite of ν1 AsO 3 symmetric stretching 2 vibration from HAsO 4 groups and AsOFe stretching vibrations from H2AsO 4 groups

877 889 ν3 AsO 3 antisymmetric stretching vibration 2 from HAsO 4 groups

951 possibly ν3 AsO 2 antisymmetric stretching vibration from H 2AsO 4 groups

1048, 1108 985 possibly ν1 SO 4 symmetric stretching vibrations 1385 1345 AsOH bending vibration from 2− HAsO 4 /H2AsO 4 groups

1635 1614 δ H2O bending vibrations

3396(broad band) composite of H 2O/OH unit/Hbond symmetric and antisymmetric stretching vibration a 2− − HFA (Theoretical) 343, 406 ν2 HAsO 4 /H 2AsO 4 symmetric bending 2− − 492 ν4 HAsO 4 /H 2AsO 4 antisymmetric bending 577 FeOH stretching vibrations/librational modes of water molecules and hydroxyl ions 613 AsOH stretching vibrations from H2AsO 4 groups 2− 696 AsOH stretching vibrations from HAsO 4 groups 742 composite of AsOH stretching vibrations from H2AsO 4 groups and AsOFe stretching 2 vibrations from HAsO 4 groups

835 composite of ν1 AsO 3 symmetric stretching 2 vibration from HAsO 4 groups and AsOFe stretching vibrations from H2AsO 4 groups

865 ν3 AsO 3 antisymmetric stretching vibration 2 from HAsO 4 groups

923, 939 ν3 AsO 2 antisymmetric stretching vibration from H 2AsO 4 groups

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985, 1230, 1271 AsOH bending vibration from 2− HAsO 4 /H2AsO 4 groups

1530 – 1621 δ H2O bending vibrations

2804 – 3714 H2O/OH unit/Hbond symmetric and antisymmetric stretching vibration Scorodite 83, 136, 182, 293 lattice mode a, b FeAsO 4 4H 2O 3 339, 383 ν2 AsO 4 symmetric bending 3 442, 468, 491 422, 456, 487 ν4 AsO 4 antisymmetric bending

580 626 FeH2O stretching vibration/librational modes of water molecules and hydroxyl ions 722 AsOFe/AsOH stretching vibration 3− 810 801, 812 ν1 AsO 4 symmetric stretching vibration 3− 827, 847, 898 831, 869, 893 ν3 AsO 4 antisymmetric stretching vibration 2− 1068 possibly ν1 SO 4 symmetric stretching vibration

1390, 1623 1468 δ H2O bending vibrations 2970, 3517 hydroxyl stretching vibrations from water molecule 2− Haidingerite 338, 323, 299 ν2 (AsO 3OH) bending vibrations c Ca(AsO 3OH)·H 2O 2− 433,420,376,369 split triply degenerate ν4 (AsO 3OH) bending vibrations 660 librational modes of water molecules and hydroxyl ions 739 δ AsOH bending vibration 2− 855 ν1 (AsO 3OH) symmetric stretching vibration 2− 886, 838 split ν3 (AsO 3OH) antisymmetric triply (shoulder), 823 degenerate stretching vibration (shoulder), 745 2842 OH stretching vibrations of water molecules 3412, 3574 stretching vibrations of the OH units c 2− Brassite 298, 274 ν2 (AsO 3OH) bending vibrations 2− 448,404, 387, 358 split triply degenerate ν4 (AsO 3OH) bending vibrations 699, 609 librational modes of water molecules and hydroxyl ions 739 δ AsOH bending vibration 2− 809 ν1 (AsO 3OH) symmetric stretching vibration 2− 878, 876, 862 split triply degenerate ν3 (AsO 3OH) antisymmetric stretching vibration 3035 OH stretching vibrations of water molecules 3305, 3314, 3387, stretching vibrations of the OH units

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3450, 3511 Pharmacolite 125, 156 lattice vibrations d Ca(AsO 3OH)·2H 2O 179, 192, 209 OCaO bending modes 287, 306 CaO stretching vibrations 2− 337,398 ν2 (AsO 3OH) bending mode 2− 416, 448 ν4 (AsO 3OH) bending mode 668, 674 684, 542 water librational modes 711, (737) 8 707, (726) 8 AsOH stretching vibrations 2− 826, 801 split doubly degenerate ν3 (AsO 3OH) antisymmetric stretching modes 8 2− 864 , (871) 865, (871) ν1 (AsO 3OH) symmetric stretching mode 8 2− 903, 893, 841 , 852, 886, (899) ν3 (AsO 3OH) antisymmetric stretching mode (899) 8 1120, 1163, 1190 1179 AsOH inplane bending vibration 1639, 1651, 1730 HOH bending modes Arseniosiderite 331, 250,227,197 lattice mode

Ca 2Fe 3(AsO 4)3O2 H2O e

3 2 389 ν2 (AsO 4 )/ δas (HAsO 4 ) bending mode 3 479, 441 ν4 (AsO 4 ) bending mode

643 535 FeOH 2 stretching vibrations 772 AsOH stretching vibrations 3 778 828 ν3 (AsO 4 ) antisymmetric stretching mode 3 852 ν1 (AsO 4 ) symmetric stretching mode 2 919 927 ν1 (HAsO 4 ) symmetric stretching mode 2 1417, 1389 ν3 (CO 3 ) antisymmetric stretching mode

1624 δ H2O bending vibration 2851

3411, 3100 OH stretching / ν H2O stretching vibrations 3576 OH stretching vibrations burgessite, 162 lattice mode

Co 2(H 2O) 4(AsO 3OH) 2 f ·H2O 233, 215 ν (O–H· · ·O) stretching vibrations 3 383, 353, 322 split doubly degenerate ν2 (AsO 4 ) bending vibrations.

492, 470, 447 split triply degenerate ν4 (δ antisymmetric) 3 437, 431 (AsO 4 ) bending vibrations 589, 557 δ AsOH bending vibrations 726, 697, 679, 655, librational modes of water molecules and 619 hydroxyl ions 741 740 ν AsOH stretching vibrations

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3 868, 836, 802 852, 830, 806 ν3 and ν1 (AsO 4 ) stretching vibrations

1707,1636 δ H2O bending vibrations 3593, 3516, 3410, 3591, 3395, 3328, ν OH stretching vibrations 3245, 2952 3204, 3185 geminite 134, 160, 171, hydrogen bonding of the water molecule g Cu(AsO 3OH)·H 2O 178, 187 213, 244, 284, Cu–O stretching and bending bands 310 2− 309, 333, 345, ν2 (δs) (AsO 3OH) split doubly degenerate 364 bending vibrations 2− 408, 424, 444, ν4 (δas ) (AsO 3OH) split triply degenerate 481, 496 bending vibrations 739, 751 741 δ As–OH bending vibrations 2− 804, 828, 876 812, 836, 859, split triply degenerate ν3 (AsO 3OH) 885 antisymmetric stretching vibrations 2− 849 851 ν1 (AsO 3OH) symmetric stretching vibration 1240, 1306, 1361, 1305 δ OH bending vibrations, overtones and 1541 combination bands

1631, 1670 ν2 (δ) HOH bending modes 2337, 2403, 2469 2289, 2433 the strong hydrogen bonded of water molecules 2820, 3037, 3190, 2737, 2855, 3235, the ν OH stretching vibrations of hydrogen 3311 3305, 3377 bonded watermolecules in the crystal structure 3452, 3520 3449,3521 the OH stretching vibrations of the hydrogen 2− bonded hydroxyls in the (AsO 3OH) units 2− mixite 386.5, 395.3, ν2 bending modes of the (AsO 3OH) (423.1 3 BiCu 6(AsO 4)3(OH) 6 423.1 and 395.3) and the (AsO 4 ) groups (386.5) h 3H 2O 3 473.7 ν4 antisymmetric bending mode of (AsO 4 ) units. 803,833 symmetric stretching vibration of the 3 protonated (AsO 4 ) units 3 854.3, 831.5, (AsO 4 ) stretching bands 809.8 867870 symmetric stretching vibration of the − protonated (H2AsO 4) units 880910 symmetric stretching vibration of the 2− protonated (HAsO 4) units 915 antisymmetric stretching vibration of 3 protonated (AsO 4 ) units 3386.7 the interlamellar water 3473.9, 3428.4 the OH stretching vibration of the hydroxyl units i Na 2HAsO 4 7H 2O 711(shoulder at 737 ν AsOH stretching vibrations

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756) 2− 835 825 ν1 (AsO 3OH) symmetric stretching vibration Sainfeldite 713 719 ν AsOH stretching vibrations of As1OH

Ca 5(HAsO 4)2(AsO 4)2 i 4H 2O 3 2− 824 824 ν1 (AsO 4 ) symmetric stretching vibration of As2OCa 3 852 852, ν3 (AsO 4 ) antisymmetric stretching mode of

As2OCa/H 2O 2− 869 869, ν1 (AsO 3OH) symmetric stretching vibration of As2OCa 3 895 895 ν3 (AsO 4 ) antisymmetric stretching mode of As1OCa j (C 6H9N2)H 2AsO 4 2735 – 3402 ν(CH 3)/ ν(NH 2)/ ν(OH) 1792 – 2553 bands of combination and harmonics 1748 δ OH bending vibrations

1301 – 1667 v(C=C), v(N=C), δ(NH 2), δ(CH 3) 1184, 1240 δ(As–O–H)

990, 1033 v(AsO 2)

865, 938 v(As(OH) 2) 581, 610 γ(AsOH)

515 ρ(AsO 2) rocking

470 ω(AsO 2) wagging 427 δ(OHAsOH) bending

396 τ(AsO 2) torsion 374 δ(OAsO) bending a This study, b Gomez et al. 9, c Frost et al. 10 , d Frost et al. 11 , e Gomez et al. 12 , f Čejka et al. 13 , g Sejkora et al. 14 , h Frost et al. 15 , i Myneni et al. 8 j Chtioui et al. 16

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