Thermodynamic and structural variations along the olivenite-libethenite solid solution

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00023272%3A_____%2F23%3A10136214" target="_blank" >RIV/00023272:_____/23:10136214 - isvavai.cz</a>

Výsledek na webu

<a href="https://ejm.copernicus.org/articles/35/157/2023/" target="_blank" >https://ejm.copernicus.org/articles/35/157/2023/</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.5194/ejm-35-157-2023" target="_blank" >10.5194/ejm-35-157-2023</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Thermodynamic and structural variations along the olivenite-libethenite solid solution

Popis výsledku v původním jazyce

Many natural secondary arsenates contain a small fraction of phosphate. In this work, we investigated the olivenite-libethenite (Cu2(AsO4)(OH)-Cu2(PO4)(OH)) solid solution as a model system for the P-As substitution in secondary minerals. The synthetic samples spanned the entire range from pure olivenite (Xlib=0) to libethenite (Xlib=1). Acid-solution calorimetry determined that the excess enthalpies are non-ideal, with a maximum at Xlib=0.6 of +1.6 kJ molMINUS SIGN 1. This asymmetry can be described by the Redlich-Kister equation of Hex= Xoli.Xlib [A+B(XoliMINUS SIGN Xlib)], with A=6.27 +- 0.16 and B=2.9 +- 0.5 kJ molMINUS SIGN 1. Three-dimensional electron diffraction analysis on the intermediate member with Xlib=0.5 showed that there is no P-As ordering, meaning that the configurational entropy (Sconf) can be calculated. The excess vibrational entropies, determined by relaxation calorimetry, are small and negative. The entropies of mixing also show asymmetry, with a maximum near Xlib=0.6. Autocorrelation analysis of infrared spectra suggests local heterogeneity that arises from strain relaxation around cations with different sizes (As5+/P5+) in the intermediate members and explains the positive enthalpies of mixing. The length scale of this strain is around 5 Å, limited to the vicinity of the tetrahedra in the structure. At longer length scales (ALMOST EQUAL TO15 Å), the strain is partially compensated by the monoclinic-orthorhombic transformation. The volume of mixing shows complex behavior, determined by P-As substitution and symmetry change. A small (0.9 kJ molMINUS SIGN 1) drop in enthalpies of mixing in the region of Xlib=0.7-0.8 confirms the change from monoclinic to orthorhombic symmetry.

Název v anglickém jazyce

Thermodynamic and structural variations along the olivenite-libethenite solid solution

Popis výsledku anglicky

Many natural secondary arsenates contain a small fraction of phosphate. In this work, we investigated the olivenite-libethenite (Cu2(AsO4)(OH)-Cu2(PO4)(OH)) solid solution as a model system for the P-As substitution in secondary minerals. The synthetic samples spanned the entire range from pure olivenite (Xlib=0) to libethenite (Xlib=1). Acid-solution calorimetry determined that the excess enthalpies are non-ideal, with a maximum at Xlib=0.6 of +1.6 kJ molMINUS SIGN 1. This asymmetry can be described by the Redlich-Kister equation of Hex= Xoli.Xlib [A+B(XoliMINUS SIGN Xlib)], with A=6.27 +- 0.16 and B=2.9 +- 0.5 kJ molMINUS SIGN 1. Three-dimensional electron diffraction analysis on the intermediate member with Xlib=0.5 showed that there is no P-As ordering, meaning that the configurational entropy (Sconf) can be calculated. The excess vibrational entropies, determined by relaxation calorimetry, are small and negative. The entropies of mixing also show asymmetry, with a maximum near Xlib=0.6. Autocorrelation analysis of infrared spectra suggests local heterogeneity that arises from strain relaxation around cations with different sizes (As5+/P5+) in the intermediate members and explains the positive enthalpies of mixing. The length scale of this strain is around 5 Å, limited to the vicinity of the tetrahedra in the structure. At longer length scales (ALMOST EQUAL TO15 Å), the strain is partially compensated by the monoclinic-orthorhombic transformation. The volume of mixing shows complex behavior, determined by P-As substitution and symmetry change. A small (0.9 kJ molMINUS SIGN 1) drop in enthalpies of mixing in the region of Xlib=0.7-0.8 confirms the change from monoclinic to orthorhombic symmetry.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10504 - Mineralogy

Projekt

—

Návaznosti

V - Vyzkumna aktivita podporovana z jinych verejnych zdroju

Rok uplatnění

2023

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

European Journal of Mineralogy

ISSN

1617-4011

e-ISSN

—

Svazek periodika

35

Číslo periodika v rámci svazku

2

Stát vydavatele periodika

DE - Spolková republika Německo

Počet stran výsledku

13

Strana od-do

157-169

Kód UT WoS článku

000956217400001

EID výsledku v databázi Scopus

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