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Silver compounds as minerals in the eastern Karkonosze granitoid pluton, Sudetes, Poland

Kozłowski Andrzej, Matyszczak Witold

Acta Geologica Polonica

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2022

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Vol. 72, no. 4

443--468

EN

Twenty silver minerals of the sulphide, arsenide, selenide, telluride, sulphosalt and chloride groups were found in 13 locations in the Variscan Karkonosze granitoid pluton. Previously only one of these minerals was known from this area. The findings include species characterized in publications as rare or exceptionally rare, e.g., muthmannite and tsnigriite. They occur in pegmatites and quartz veins; their parageneses are described. The studies include determination of chemical compositions, formulae calculations and recording of XRD patterns. Inclusion studies in paragenetic quartz indicate that they crystallized from epithermal fluids with a common but low component of CO2. The results suggest that the minerals formed from trace elements (Ag included) in the Karkonosze granitoid due to very local degrees of recrystallization of the host granitoid.

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Prawidłowości występujące w diagramach fazowych układów potrójnych Tl-Te-M

Sztuba Z.

Wiadomości Chemiczne

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2009

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[Z] 63, 9-10

803-818

EN

The aim of this work was to present regularities in the phase equilibria in the Tl2Te-MxTey systems, where M stands for metals belonging to periods IV–VI and groups 11–15 of Periodical Table. Additionally, the Tl2Te-As2Te3, Tl2Se-Bi2Se3 and Tl2Te-Tl2Se systems were considered. The phase diagrams are presented in a simple form in Fig. 1 for the following systems: Tl2Te-Cu2Te [1], Tl2Te-ZnTe [2], Tl2Te-CdTe [3], Tl2Te-HgTe [4–6], Tl2Te-In2Te3 [7, 8], Tl2Te-PbTe [9], Tl2Se-Tl2Te [10], Tl2Se-Bi2Se3 [11], Tl2Te-Ga2Te3 [12], Tl2Te-Ag2Te [13], Tl2Te-SnTe [14], Tl2Te-Sb2Te3 [15], Tl2Te-Bi2Te3 [16], Tl2Te-GeTe [17] and Tl2Te-As2Te3 [18]. The state of phase equilibria illustrated by the phase diagram depends on the tendency to chemical compounds formation by the components of a system. This tendency can be observed in the number of compounds formed, their melting points and the type of melting process (congruent or noncongruent). The tendency to compounds formation or at least the melting points of the compounds formed increases with increase of the atomic number of the metal within a group of systems containing as the second component tellurides of metals from a given group in the Periodic Table. There is no correlation between type of phase diagram and metal position in a given period. Thus, increasing the number of outer shell electrons for consecutive elements M of the same group does not affect the tendency to the chemical compounds formation. Regardless of the compounds number – terminal solid solutions have been observed only in some telluride systems. The data in Table 1 show that solid solutions are formed when the value of relative difference between thallium and metal M radii is smaller than 10%. All salt systems arranged in decreasing order of their ionic potentials ratios μ_Tl/μ_M are presented in Table 2. While this ratio decreases the tendency to congruent compounds formation increases abruptly from 1 to 2 at the value of a ratio equal to 0.21, exactly as in the case of typical salts [20]. The influence of molecular stability coefficients on the number of compounds existing in the system (Table 3) has been discussed. The greater difference is between the values of molecular stability coefficients the more compounds are formed. The impact of a common anion change on the shape of phase diagrams for the systems Tl2Te-Bi2Te3 [16] and Tl2Se-Bi2Se3 [11] as well as the regularities in the chalcogenide systems with a common cation has been described. All compounds being components of the systems presented in this work are listed in Table 4.

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Local electronic and charge state of iron in FeTe2

Stanek J., Fornal P.

Nukleonika

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2004

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Vol. 49,suppl.3

63-65

EN

From 57Fe Mössbauer spectrum of FeTe2 taken in high external magnetic field (B = 4.6 T), the sign of electric field gradient was determined as negative, with an asymmetry parameter of 0.2. A comparison of these data with results of calculation of the electric field gradient within point charge model suggests the lattice character of electric field gradient with some contribution from covalency effects. The effective magnetic field acting on 57Fe is less than the applied, which points out the diamagnetic Fe+2 state of iron. This "electronic state" is in a contradiction to Fe+3 "charge state" concluded from 125Te experiments on 3d transition metal ditellurides as well as from 57Fe quadrupole splitting and isomer shift.