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The FeS2–Ag–Pt–As system was studied using hydrothermal thermogradient synthesis (with internal sampling) of pyrite crystals at a temperature of 500°C and pressure of 1 kbar in ammonium chloridebased solutions. The modes of occurrence of precious metals (PM) were determined using atomic absorption spectrometry (AAS) in its version of statistical selections of analytical data on single crystals (SSADSC), electron microprobe analysis (EMPA), scanning electron microscopy with energy-dispersive spectrometry (SEM-EDS), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The concentration of Pt in its structural mode in pyrite is as high as 10–11 ppm and is practically not correlated with the As concentration. The dualistic distribution coefficient of Pt between pyrite and hydrothermal solution is 21 ± 7 for the structural mode and 210 ± 80 for the surface-related mode of this element. No inclusions of either any Pt-bearing minerals or Pt itself was detected. Platinum is an element highly compatible with hydrothermal pyrite and is different in this sense from gold, and pyrite is underestimated as a potential concentrator of platinumgroup elements (PGE). The distribution of Ag in pyrite is highly heterogeneous. The likely reason for this is that the Ag solid solution cannot be quenched, and hence, the Ag concentrations broadly vary and are very unsystematically distributed in natural pyrite crystals. Assuming this hypothesis, the limit for Ag accommodation in FeS2 can be estimated using SSADSC at 0.09 ± 0.06 wt % under the experimental parameters, and the distribution coefficient of the structural Ag mode is thereby evaluated at 1400 ± 700. When crystallizing together with FeS2 proustite (Ag3AsS3) near its melting point, forms mixtures with dervillite (Ag2AsS2), in which Ag deficit is counterbalanced by excess divalent As. The limit of As incorporation into pyrite under these conditions is ≤0.1 wt %. SEM-EDS and XPS data indicate that the surface phases are of three types. In the course of crystal growth, practically two-dimensional nonautonomous phases (NP) are aggregated into submicroscopic and micrometer-sized crystalline bodies (mesocrystals) that largely inherit their unusual minor-element composition from NP and are enriched in Ag, Pt, As, and other minor elements. NP and mesocrystals are enriched in Al, which was transferred into them from the Al-bearing Ti alloy of the reaction containers. Silver occur in the volume of the crystals and on their surface as monovalent silver sulfide. Arsenic was detected mostly in the form of di- and trivalent arsenic sulfides. Pentavalent arsenic oxide was identified only on the surface of the crystals and can be easily eliminated by ion milling.

The spectral - structural features of the rare silver arsenic (Ag-As) sulfosalts, proustite, Ag3AsS3, and the extremely scarce smithite, AgAsS2, trechmannite, AgAsS2 and xanthoconite, Ag3AsS3, were studied by the μ-Raman technique. Stretching - bending vibrations of the pyramidal isolated and interconnected AsS3 groups were responsible for the Raman spectra of the studied sulfosalts. The symmetric and asymmetric stretching modes appear between 380 and 350 cm− 1, whereas those of bending (S As S) vibrations between 335 and 280 cm− 1. The As S longer bond lengths absolutely demonstrate the red shift (i.e. decrease in energy) from xanthoconite to trechmannite, smithite and proustite and the lowering in FWHM in comparable vibrational modes.

Laser stimulated elasto-optical effects in the proustite crystals (Ag 3 AsS 3 ) under influence of coherent bicolor laser treatment with simultaneous illumination by low power He-Ne laser beams have been discovered for the first time. The changes of the piezo-optics have been explored during the first 3 – 5 min. of illumination by two bicolor coherent nanosecond laser beams at 1064 nm and 532 nm. The changes of the piezo-optical coefficients for the bicolor behaviors of the piezo-optical coefficients versus the photoinduced beam diameters and power densities are explored. Three different laser wavelengths (633 nm, 1064 nm, 3390 nm) have been applied for the probing of the photoinduced changes. The space profiles of the probing beams demonstrate an existence of the quasi-periodic gratings structure. It is shown that the probing beams play an effective role in the observed laser stimulated effects. The principal role here is played by Ag ions participating in the ionic conductivity which favor an internal dc-electric field and related photorefraction.

The spontaneous formation of self-assembled and/or self-organized patterns is a fundamental and technologically significant topic. This process is achieved via a phenomenon called dewetting, should it be thermally induced, or caused by laser exposure. Although dewetting seems to be a well-known phenomenon for metallic and polymeric thin films, no proper investigation regarding glassy thin films seems to have been done. Thus, in the present study we try to elaborate on the process of thermal dewetting applied to glassy thin films of the system Agx(As20S80)100−x.

The present study shows the characterization of a zinc concentrate collected at Hidalgo, Mexico, in order to identify its mineralogical species and to propose a leaching methodology for silver recovery. The results obtained by X-Ray Diffraction (XRD) show Sphalerite (ZnS) as the mineralogical matrix and silver into the specie proustite (Ag3AsS3). The techniques of Scanning Electron Microscopy-Energy Dispersive Microanalysis (SEM-EDS) and Polarized Optical Microscopy (POM) identified the presence of sulfides of Fe, Cu, Pb and Zn, in addition to silicates and feldspar. The proposed dissolution method of Ag(I) was carried out with [S2O3 2−] = 0.5 M and [NaOH] = 0.1 M to regulate the medium at pH = 9 for 12 h at 298 K. Oxidation of the concentrate was favored by injection of O2 to a partial pressure of 1 atm. Monitoring of the reaction was carried out by reading the [Ag] and [As] by AAS.

A new solvothermal method has been successfully prepared crystalline proustite Ag3AsS3 (1) by the reactions of As2O3, AgNO3 and elemental sulfur in diaminopropane (dap) at 160 °C for 3 days. The crystalline material of 1 was characterized by single crystal X-ray diffraction, powder X-ray diffraction, UV–visible diffuse reflectance spectroscopy, scanning electron microscopy and nonlinear optical determination. The three-dimensional polar framework of 1 is constructed by the linkages of unsymmetrical [AsS3] trigonal pyramids and T-shaped [AgS3] units via bridging S atoms. The absorption edge of 1 is 2.03 eV, exhibiting properties of the semiconductor, and its theoretical band structure has also been studied. Photocatalytic experiments have shown the ability of 1 in the degradation of methylene blue (MB) under visible light (λ > 420 nm).

The effect of high pressure (up to 40 GPa) and alternating electric field frequency (100 Hz-500 kHz) on the electrical properties of synthesized single-crystal proustite Ag3AsS3 is studied. The behavior of real and imaginary parts of impedance upon an increase in pressure confirms earlier data on the closing of valence and conduction zones, and on the material's transition to the metal state at ∼30 GPa. © 2013 Allerton Press, Inc.

Manganoquadratite, ideally AgMnAsS3, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as dark gray, anhedral to subhedral grains up 0.5 mm across, closely associated with alabandite, Mn-rich calcite, Mn-rich sphalerite, proustite, pyrite, pyrrhotite, tennantite, argentotennantite, stannite, and other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S. Manganoquadratite is opaque with a metallic luster and possesses a reddish-brown streak. It is brittle, the Vickers microhardness (VHN10) is 81 kg/mm 2 (range 75–96) (corresponding Mohs hardness of 2–2½). The calculated density is 4.680 g/cm 3 (on the basis of the empirical formula). In plane-polarized reflected light, manganoquadratite is moderately bireflectant and very weakly pleochroic from dark gray to a blue gray. Internal reflections are absent. Between crossed polars, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 29.5, 31.8 (471.1 nm), 28.1, 30.5 (548.3 nm), 27.3, 29.3 (586.6 nm), and 26.0, 28.2 (652.3 nm), respectively. Manganoquadratite is tetragonal, space group P4322, with unit-cell parameters: a = 5.4496(5), c = 32.949(1) A, V = 978.5(1) A 3 , c:a = 6.046, Z = 8. The structure, refined to R1 = 0.0863 for 907 reflections with Fo > 4σ(Fo), consists of a stacking along [001] of alabandite-like Mn2S2 layers connected to each to other by a couple of AgAsS2 sheets where As 3+ forms typical AsS3 groups, whereas Ag + cations are fivefold coordinated. The six strongest lines in the observed X-ray powder-diffraction pattern [d in A (I/I0) (hkl)] are: 3.14 (60) (116), 2.739 (50) (0 0 12), 2.710 (100) (200), 1.927(70) (2 0 12 + 220), 1.645 (25) (3 0 16), and 1.573 (20) (2 2 12). Electron microprobe analyses gave the chemical formula (on the basis of six atoms) (Ag0.95Cu0.05)Σ=1.00 (Mn0.96Pb0.04)Σ=1.00(As0.87Sb0.14)Σ=1.01S2.99, leading to the simplified formula AgMnAsS3.

The present paper reports a crystal-chemical study of minerals belonging to the proustite–pyrargyrite group by evaluating 32 natural samples of proustite and 27 samples of pyrargyrite from different localities that have variable chemical compositions. The unit-cell parameters were modeled as a function of the Sb contents. The a parameter is strongly influenced by the As ↔ Sb substitution, whereas the influence on the c parameter is very minor (nearly constant trend). The following equations were obtained from the linear fitting of the data: \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \begin{eqnarray*}&&\mathit{a}\_{pred}\ =\ 10.8433(3)\ +\ 0.2019(4)Sb\ (apfu)\\&&\mathit{c}\_{pred}\ =\ 8.7189(6)\ +\ 0.0059(9)Sb\ (apfu)\\&&\mathit{V}_{pred}\ =\ 887.77(7)\ +\ 34.0(1)Sb\ (apfu).\end{eqnarray*} \end{document} The crystal structure of the members of the proustite–pyrargyrite solid solution consists of two sets of spiral chains parallel to the c -axis. Each chain contains alternating Ag and S atoms, with each chain being connected by As and Sb atoms, which are the apices of flat pyramidal AsS3/SbS3 groups. Each S atom is part of a different Ag-S chain. The compositional data support the concept that proustite–pyrargyrite solid solutions re-equilibrate and exsolve to near end-member upon cooling. Examples of intermediate compositions are rare in nature and must have quenched above the solvus.

For the first time, we consider the possibility of formation of AB3X3 compounds in the A2X3-B2X (A and B are different elements; X = S, Se, Te) systems under standard conditions. For the prediction, we use an ad hoc information analysis system that combines the subsystem of databases on properties of inorganic substances and materials and programs for data analysis on the basis of computer training algorithms.

Single crystals of proustite Ag{sub 3}AsS{sub 3} have been characterised by impedance spectroscopy and single-crystal X-ray diffraction in the temperature ranges of 295-543 and 295-695 K, respectively. An analysis of the one-particle potential of silver atoms shows that in the whole measuring temperature range defects in the silver substructure play a major role in the conduction mechanism. Furthermore, the silver transfer is equally probable within silver chains and spirals, as well as between chains and spirals. The trigonal R3c room temperature phase does not change until the decomposition of the crystal. The electric anomaly of the first-order character which appears near 502 K is related to an increase in the electronic component of the total conductivity resulting from Ag{sub 2}S deposition at the sample surface. - Joint probability density function map of silver atoms at T=695 K.

The influence of modulated crucible rotation on the axial distribution of Cu, Mg and Si impurities in proustite single crystals grown by the Stockbarger method using ACRT is studied in a wide range of Taylor numbers (1.9·105 < Ta < 7.12·107). The impurity content in the upper part and in the tail portion of the grown crystals is measured using X-ray-phase analysis. Micro and macrostriations are observed in the grown crystals. The wavelengths of impurity content fluctuations have been determined. The microfluctuations of axial impurity content are caused by modulated crucible rotation. The studies have revealed that the ACRT provides an effective removal of impurities from the main part of the grown crystal at high intensity of melt stirring, and consequently, the ACRT can be applied validly to decrease the impurity content during the growing of high-quality proustite single crystals. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Raman spectra of 17 fahlore samples (tetrahedrite-tennantite solid solution series) and 3 samples of the pyrargyrite-proustite solid solution series were recorded. The fundamental stretching and bending vibrations of the pyramidal (Sb, As)S 3 groups occur between 200 and 400 cm −1 . The position, shape, relative intensity and appearance of the bands vary depending upon the Sb/(Sb+As) ratios of both mineral series. The symmetric stretching mode (ν 1 ) shows a two-mode behavior in the tetrahedrite-tennantite solid solution series, whereas one-mode behavior is observed in all other cases. The excellent correlations between the positions of the vibrational modes and the Sb/(Sb+As) ratio, can be applied to determine the composition of the investigated sample by at least one band in the Raman spectrum of the mineral.

Extreme silver enrichment at the surface of the complex sulphide, tennantite (ideal formula: Cu12As4S13), occurs following exposure to alkaline solutions, and involves the development of an Ag-rich sulphide surface species. The tennantite has a low bulk Ag content of 0.3 at.%, and a percentage surface enrichment of Ag is thirty-six times that of the bulk. The techniques of X-ray photoelectron spectroscopy (XPS) and reflection extended X-ray absorption fine structure spectroscopy show the new phase to be a Ag sulphide species compositionally similar to cupriferous proustite ((Cu,Ag)3AsS3). Solution experiments and XPS depth profiling show that the surface is most depleted in Cu and Zn, and enriched in Ag compared to the bulk tennantite. Selective dissolution and reprecipitation at the tennantite surface cannot explain the enrichment of Ag relative to the bulk. Migration must have occurred and could have been driven by the leaching out of Cu which produces a metal-depleted surface, coupled to the relative incompatibility of Ag in the tennantite lattice. To account for the extreme enrichment at the surface, Ag must have diffused from depths of up to 9 nm, probably via structural weaknesses and vacancies in the tennantite lattice.

The effect of the melt stirring rate on the radial distributions of Cu, Sb, and Mg impurities in proustite single crystals grown by the Stockbarger method using accelerated crucible rotation and on the optical quality of the crystals is studied in a broad range of Taylor numbers: from 1.9 × 105 to 7.12 × 107. The radial impurity distributions, measured by electron probe x-ray microanalysis, show random oscillations. The accelerated crucible rotation technique makes it possible to reduce the impurity content of proustite and grow optically superior crystals.

Infrared (IR)-induced two-photon absorption (TPA) in synthesized PbO–Ga2O3–Bi2O3–CdO (PGBC) glasses doped by Eu3+ and Tm3+ rare earth (RE3+) ions was investigated. Temperature-dependent measurements of TPA were carried out in the mid-IR spectral range. A CO pulsed laser (λ = 5.5 μm, energy power density up to 3.8 GW/cm2 per pulse with picosecond pulse duration) was applied as the source of photoinducing IR radiation. An optical parametrical generator cut from a proustite crystal was used as the source of the fundamental TPA beam within the 3–7.5 μm spectral range. Absolute values of the TPA coefficients were more than 13% higher than corresponding values obtained for other similar glasses (As2Te3–CaCl2–PbCl2 [1] or Sb2Se3–BaCl2–PbCl2 [2]). The PGBC system investigated possessed a shorter time response (about 12 ps) compared with other IR nonlinear optical glasses. It was also established that all nonlinear optical susceptibilities were dependent on the type of RE3+ ion. A maximum value of the TPA was achieved for the glasses doped by Tm3+. The TPA values increased significantly below 45 K. Ab initio molecular dynamics and quantum chemical simulations were performed in order to evaluate the possible role of electron–phonon anharmonic interactions in the observed phenomena. The influence of the external CO photoinduced pump beam through the photoinduced electrostricted anharmonic electron–phonon interactions was simulated. A decrease of picosecond delaying time response compared with other glasses was achieved. To obtain independent confirmation of the observed dependencies, measurements were carried out of χxxxx(E) during the external IR pumping. The measured and theoretically calculated dependencies of the third-order susceptibilities were also compared. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The vibrational (Raman and far infrared) spectra of four M3IMIIIS3 type synthetic minerals (proustite, Ag3AsS3; ellisite, Tl3AsS3; pyrargyrite, Ag3SbS3; stibioellisite, Tl3SbS3) in the region from 600 to 100 cm−1 (Raman) and 600 to 20 cm−1 (far infrared) were investigated. Their infrared and Raman spectra were compared with corresponding vibrational spectra of natural orpiment, As2S3, and stibnite, Sb2S3. In general, rather expressed similarity between the Raman spectra of the M3IAsS3 type synthetic minerals, and particularly between the M3ISbS3 type synthetic minerals (MI = Ag or Tl) was observed. This is, most probably, due to the presence of the MIIIS3 pyramids (MIII = As or Sb) as main structural units in all minerals. The observed similarity between the Raman spectra of the M3IAsS3 type minerals and the corresponding spectrum of orpiment, As2S3 (also built up of MIIIS3 pyramids), justifies the treatment of those pyramids as a main vibrational units. The agreement between the Raman spectra of M3ISbS3 type minerals, on the one hand, and the Raman spectrum of stibnite, Sb2S3, on the other hand, is even much more pronounced. It was found, however, that the bands in the infrared spectra in the studied M3IMIIIS3 type minerals, besides the sensitivity to the MIII atom (As or Sb), are significantly influenced by the nature of the MI atom (Ag or Tl). This is most probably related to the different extent of the covalent character of the AgS bonds compared to the TlS bonds.

The influence of the intensity of melt stirring on the radial impurity distribution and optical quality of proustite single crystals grown by the Stockbarger method using ACRT is studied by the example of Cu, Sb and Mg impurities. We report results obtained in a wide range of Taylor numbers (1:9 � 10 5 oTao7:12 � 10 7 ). The studies revealed that the ACRT can be applied validly to decrease the impurity content during the growing of high-quality single crystals. r 2003 Elsevier Science B.V. All rights reserved.

The nature of phase transitions in natural and synthetic proustite, Ag3AsS3, has been studied in darkness above 300 K and compared with its natural counterpart pyrargyrite, Ag3SbS3. The behavior of proustite is characterized by silver ion mobility within the structure. Proustite and (to a lesser extent) pyrargyrite were investigated as a function of temperature by x-ray and neutron powder diffraction, dielectric spectroscopy, and dynamic mechanical analysis. At 305 K (280 K for pyrargyrite) proustite undergoes a second-order phase transition, exhibiting a positive nonsymmetry breaking spontaneous strain of the unit cell, with thermal expansion along [001] changing from negative to positive. This strain results from the onset of thermally induced hopping of silver ions, as revealed by impedance spectroscopy. It may be described as an almost undamped Debye oscillator, which is not present below Tc (305 K) with an activation energy of 0.42 eV (0.40 eV for pyrargarite). Around 420 K the high-frequency conduct...

The influence of the intensity of melt stirring on the optical quality of proustite single crystals is studied in the range of Taylor numbers 1.9×105 4×106. Within the studied range of the Taylor numbers, the increase of the intensity of melt stirring is shown to lead to the improvement of the optical quality of proustite single crystals. The technique for the growing of enlarged proustite single crystals by the Bridgman–Stockbarger method using modulated rotation of growth crucible has been devised.

The effect of Si content on the optical quality of proustite single crystals grown by the Stockbarger method using accelerated crucible rotation was studied. The rate of melt stirring was varied in the range corresponding to Taylor numbers from 1.9 × 105 to 7.26 × 107. It was shown that the Si content of the crystals could rise in different stages of the preparation process. Si contents above 5 × 10–3 wt % impaired the optical perfection of proustite crystals, independent of the rate of melt stirring.

Red block crystals of the title compound are solvothermally synthesized from As2O3, AgNO3, and sulfur in diaminopropane (thick Pyrex tube, 160 °C, 3 d, 73% yield).

An updated thermodynamic database for Ag2S–Cu2S–ZnS–Sb2S3–As2S3 sulfides and sulfosalts applicable to temperatures above 119°C is developed to calculate phase relations for polybasite-pearceite- and fahlore-bearing assemblages. It is based on pre-existing and new constraints on activity-composition, Ag–Cu and As–Sb partitioning, and other relations, and on experiments (200–300°C, evacuated silica tubes) conducted to define the stability of the polybasite-pearceite [(Ag1−x,Cux)16(Sb1−y,Asy)2S11] + ZnS sphalerite assemblage with respect to assemblages containing (Ag,Cu)2S sulfides coexisting with (Cu, Ag)10Zn2(Sb,As)4S13 fahlore sulfosalts. It was found that the thermodynamics of mixing of bcc– and hcp–(Ag,Cu)2S solutions, which are fast-ion conductors, may be described by using site multiplicities of metals αAg,Cu > 2 and temperature-dependent regular solution parameters. We obtained estimates for the Gibbs energies of formation for Ag16Sb2S11 and Cu16Sb2S11 polybasite endmembers from the simple sulfides (Ag2S, Cu2S, and Sb2S3) of −30.79 and −4.07 kJ/gfw at 200°C, and −32.04 and −0.59 kJ/gfw at 400°C, respectively, that are about one half kJ/gfw more positive and about 6 kJ/gfw more negative than those estimated by Harlov and Sack (1995b) . The corresponding estimates for formation energies of Ag10Zn2Sb4S13 and Cu10Zn2Sb4S13 fahlores (−20.29 and −105.29 kJ/gfw at 200°C and −23.72 and −105.76 kJ/gfw at 400°C) are comparable to, and roughly 110 kJ/gfw more positive than, the corresponding estimates of Ebel and Sack (1994) . We also determined that the Gibbs energies of the As–Sb exchange reactions: 1 4 Ag 10 Zn 2 Sb 4 S 13 + 1 2 Ag 16 As 2 S 11 = 1 2 Ag 16 Sb 2 S 11 + 1 4 Ag 10 Zn 2 As 4 S 13 Sb–fahlore pearceite polybasite As–fahlore and Ag 3 SbS 3 + 1 2 Ag 16 As 2 S 11 = 1 2 Ag 16 Sb 2 S 11 + Ag 3 AsS 3 pyrargyrite pearceite polybasite proustite are, respectively, 8.75 and 0.40 kJ/gfw in the range 150–350°C, and these predictions are consistent with As–Sb partitioning relations observed in nature and produced in laboratory studies. Finally, we obtain estimates for the Gibbs energies of formation of Cu10Fe2Sb4S13 and Ag10Fe2Sb4S13 fahlores (−63.92 and +11.46 kJ/gfw at 200°C and −75.73 and −3.31 kJ/gfw at 400°C).

${}^{75}\mathrm{As}$ NQR spectra and spin-lattice relaxation time ${T}_{1}$ have been measured between room temperature and 4.2 K in a proustite $({\mathrm{Ag}}_{3}{\mathrm{AsS}}_{3})$ single crystal. In agreement with x-ray scattering data we find that the phase between ${T}_{I}=60\mathrm{K}$ and ${T}_{L}=49\mathrm{K}$ is triple-q $(3\ensuremath{-}q)$ incommensurably modulated. Our results show unambiguously that we deal here with three independent noncoplanar incommensurate modulation wave vectors. Such a phase seems to be unique in a sense that other phases with three incommensurate modulation waves known so far (e.g., in charge-density-wave systems) are either a superposition of differently oriented $1\ensuremath{-}q$ modulated domains, or the three modulation waves are confined to a plane and are thus not independent. In addition the ${}^{75}\mathrm{As}$ NQR line shape suggests that the phase just below ${T}_{I}$ is a single-q $(1\ensuremath{-}q)$ modulated stripe phase. This is confirmed by the variation of ${T}_{1}$ over the NQR line in the $1\ensuremath{-}q$ and $3\ensuremath{-}q$ phases. On further cooling further into the incommensurate phase the volume fraction of the $3\ensuremath{-}q$ phase gradually increases and the crystal becomes fully $3\ensuremath{-}q$ modulated about 2 K below ${T}_{I}.$ The nonclassical critical exponents for the amplitude of the order parameter were determined to be ${\ensuremath{\beta}}_{1}=0.3\ifmmode\pm\else\textpm\fi{}0.02$ in the $1\ensuremath{-}q$ stripe phase and ${\ensuremath{\beta}}_{3}=0.4\ifmmode\pm\else\textpm\fi{}0.02$ in the $3\ensuremath{-}q$ phase. On approaching the lock-in transition temperature in the low-temperature part of the $3\ensuremath{-}q$ incommensurate phase the phases of the modulation waves become nonlinear functions of the corresponding spatial coordinates, resulting in sharp peaks superimposed on the broad bell-shape frequency distribution. A comparison between experimental and theoretical line shapes allowed for a quantitative determination of the temperature dependence of the soliton density.

Experimental Ag-Cu exchange equilibria (evacuated silica tubes; variable mass ratio) involving proustite (Ag,Cu) 3 AsS 3 , smithite AgAsS 2 , pearceite (Ag,Cu) 16 As 2 S 11 , lautite CuAsS, and sinnerite Cu 6 As 4 S 9 are reported over the temperature range 150-350 degrees C. Lautite and sinnerite are found to take in negligible amounts of Ag (below the detection limit of the microprobe), even at 350 degrees C. Similarly smithite is found to take in 3 (Sb,As)S 3 and polybasite-pearceite (Ag,Cu) 16 (Sb,As) 2 S 11 , a model is calibrated which reflects both the Ag-Cu and As-Sb mixing properties of the pyrargyrite-proustite solid solution over the temperature range 120-400 degrees C. Explicit provision for site distortion in proustite resulting from the Cu+ for Ag+ substitution (or Ag+ for Cu+ substitution) is made by assuming that the standard state properties of the Ag-proustite and Cu-proustite end members are linearly dependent on the Cu/(Cu+Ag) ratio. Cu substitution in pyrargyrite-proustite is both asymmetric and substantially non-ideal (W (super Pyr-Prs) CuAg = 21.0; W (super Pyr-Prs) AgCu = 11+ or -0.5 kJ/gfw) as opposed to As-Sb mixing along the proustite-pyrargyrite join, which has been found to be both more symmetric and more ideal (W (super Pyr-Prs) AsSb = 6.00+ or -0.60 kJ/gfw). The reciprocal energy, Delta G rec , between proustite and pyrargyrite is found to approximate 0. Ag-Cu exchange experiments between pearceite grains and equimolar powder mixtures of proustite and sinnerite are used to define equilibrium compositions for a three-phase region involving proustite, pearceite and sinnerite over the temperature range 150-350 degrees C.

Temperature dependences of acoustic emission and relative intensity of some structural x-ray peaks for proustite (Ag3AsS3) samples are investigated in the temperature range 100–300 K. Anomalous behavior of the obtained dependences is observed at T∼150 K. The experimental results have been analyzed by using different models of positional disorder of the silver sublattice. The entire body of the obtained data can be explained assuming that an increase in temperature starting from T∼150 K leads to predominant disordering of the part of the cationic sublattice of proustite, that is formed by right spirals (AgS)∞.

The effect of continuous heating on the characteristics of phase transformations in proustite (Ag3AsS3) is established. It is shown that continuous heating, like continuous cooling, stimulates structural remodeling, in this case reducing the temperature of the known phase transitions.

Optical damage induced by infrared irradiation of proustite is investigated with holographic methods and photoelectron spectroscopy. Holographic writing results in thin absorption gratings located on the surface. This phenomenon is traced back to formation of Ag2S by a decomposition reaction on the surface of aged proustite crystals and generation of a metastable state of Ag2S by infrared light. The writing and erasing kinetics is studied by two-beam mixing with Nd3+-doped yttrium aluminium garnet laser radiation with λ = 1.06 μm. The metastable absorption gratings induced on the surface reach a diffraction efficiency of a few per cent and have a storage time of 104.

Far infrared (IR) reflectivity spectra of thallium arsenic selenide (TAS) are measured for the first time, for both polarizations parallel and perpendicular to the c-axis, at 7, 100 and 250 K, in the frequency range 10–600 cm−1. The phonon modes are classified within their symmetry species, their frequencies and oscillator strengths are calculated from the analysis of the experimental spectra. Splitting of several low-frequency optical modes indicates the possibility of a structural modification below 100 K. On the basis of an internal and external mode analysis and by comparison with similar compounds such as proustite and pyrargyrite, the origin of the various vibrational modes is discussed.

We have observed the NMR lineshape for 109 Ag in the paraelectric, incommensurate and commensurate phases of the 3 q incommensurate insulator proustite (Ag 3 AsS 3 ). In the paraelectric phase we observed discrete narrow lines representative of the six Ag sites in the unit cell. In the incommunsurate region the narrow lines are replaced by two broad, featureless peaks, typical of a 3 q incommensurate modulation. This is the first observation of such incommensurate line broadening for a dipolar nucleus in an insulator. In the commensurate region a larger number of discrete lines are observed, indicative of an increase in the size of the unit cell.

Structural characteristics and charge transfer processes in Ag3AsS3 crystals were studied by dielectric spectroscopy and scanning electron microscopy methods; the relaxation parameters of the system were evaluated.

The reactivity of the ruby silver minerals proustite (3Ag(2)S⋅As(2)S(3)) and pyrargyrite (3Ag(2)S⋅Sb(2)S(3)) was studied with two types of electrodes: a carbon-paste electroactive electrode (CPEE) and a paraffin-impregnated graphite electrode (PIGE). Polycrystalline samples of α-Ag(2)S (acanthite), As(2)S(3) (orpiment), Sb(2)S(3) (stibnite), Ag(3)AsS(3) (proustite), Ag(3)SbS(3) (pyrargyrite), and three samples of the proustite-pyrargyrite solid solution series were synthesized from pure elements by a solid-state reaction method. Phase identification of samples was carried out by XRD and chemical homogeneity was checked by SEM-EDS. Besides, sulfosalts were characterized by diffuse reflectance spectroscopy (DRS). Flat-band and formal potentials of sulfosalts were determined by the Mott-Schottky method and differential pulse abrasive stripping voltammetry, respectively. Band structure, bonding and solid-state structure are considered to investigate the oxidation and reduction of the solids. A ligand-to-metal charge transfer (LMCT) transition from the AsS(3) (or SbS(3)) group to Ag is related to ease of reducing the pyrargyrite-proustite series. Despite the increase in the amount of As (Sb) in Ag(3)SbS(3) (Ag(3)AsS(3)), reactivity is similar due to the similarity of the solid-state structures, and the same oxidation states of S, As, Sb and Ag species in the lattice. However, the nature of the pnictogen (As or Sb) changes the position of the conduction and valence band edges and modulates the reactivity of the pyrargyrite-proustite series. Anodic dissolution occurs by hole transfer from the top of the valence band that is formed mainly by the states of the AsS(3) and SbS(3) groups. Meanwhile, silver reduction occurs by electron transfer from the Ag 5s orbitals located at the bottom of the conduction band. The difficulty in dissolving proustite and pyrargyrite in cyanide is related to the presence of pyramidal AsS(3) and SbS(3) groups in these sulfosalts.