The position of vanadium in the crystal structure of zoisite, variety tanzanite: Structural refinement, optical absorption spectroscopy and bond-valence calculations

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216224%3A14310%2F23%3A00132735" target="_blank" >RIV/00216224:14310/23:00132735 - isvavai.cz</a>

Výsledek na webu

<a href="https://doi.org/10.1180/mgm.2023.48" target="_blank" >https://doi.org/10.1180/mgm.2023.48</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1180/mgm.2023.48" target="_blank" >10.1180/mgm.2023.48</a>

Jazyk výsledku

angličtina

Název v původním jazyce

The position of vanadium in the crystal structure of zoisite, variety tanzanite: Structural refinement, optical absorption spectroscopy and bond-valence calculations

Popis výsledku v původním jazyce

Vanadium is the dominant trace element and chromophore in tanzanite, the most valued gemmological variety of zoisite. The structure of zoisite–tanzanite was obtained by structural refinement to assess the vanadium location in the zoisite structure. However, the small V content in tanzanite evidenced by electron microprobe and laser ablation inductively coupled plasma mass spectrometry limits the exact determination of the V position in the zoisite structure. Structural refinement revealed that the average bond length of the less distorted M1,2O6 octahedron is below 1.90 Å, and M3O6 has slightly longer bonds with an average of ca. 1.96 Å. The M1,2 site is slightly overbonded with a bond-valence sum (BVS) of 3.03 vu, whereas M3 is slightly underbonded (BVS = 2.78 vu). Optical absorption spectra revealed that most V is trivalent, but a small portion is probably in a four-valent state. Therefore, crystal field Superposition Model and Bond-Valence Model calculations were applied based on several necessary assumptions: (1) V occupies octahedral sites; and (2) it can occur in two oxidation states, V3+ or V4+. Crystal field Superposition Model calculations from the optical spectra indicated that V3+ prefers occupying the M1,2 site; the preference of V4+ from the present data was impossible to determine. Bond-Valence Model calculations revealed no unambiguous preference for V3+, although simple bond-length calculation suggests the preference of the M3 site. However, it is quite straightforward that the M1,2 site is better suitable for V4+. If the possible octahedral distortion is considered, the M1,2O6 octahedron is subject to a smaller change in distortion if occupied by V3+ than the M3O6 octahedron. Consequently, considering the results of both the crystal field Superposition Model and Bond-Valence Model calculations, we assume that both V3+ and V4+ prefer the M1,2 site.

Název v anglickém jazyce

The position of vanadium in the crystal structure of zoisite, variety tanzanite: Structural refinement, optical absorption spectroscopy and bond-valence calculations

Popis výsledku anglicky

Vanadium is the dominant trace element and chromophore in tanzanite, the most valued gemmological variety of zoisite. The structure of zoisite–tanzanite was obtained by structural refinement to assess the vanadium location in the zoisite structure. However, the small V content in tanzanite evidenced by electron microprobe and laser ablation inductively coupled plasma mass spectrometry limits the exact determination of the V position in the zoisite structure. Structural refinement revealed that the average bond length of the less distorted M1,2O6 octahedron is below 1.90 Å, and M3O6 has slightly longer bonds with an average of ca. 1.96 Å. The M1,2 site is slightly overbonded with a bond-valence sum (BVS) of 3.03 vu, whereas M3 is slightly underbonded (BVS = 2.78 vu). Optical absorption spectra revealed that most V is trivalent, but a small portion is probably in a four-valent state. Therefore, crystal field Superposition Model and Bond-Valence Model calculations were applied based on several necessary assumptions: (1) V occupies octahedral sites; and (2) it can occur in two oxidation states, V3+ or V4+. Crystal field Superposition Model calculations from the optical spectra indicated that V3+ prefers occupying the M1,2 site; the preference of V4+ from the present data was impossible to determine. Bond-Valence Model calculations revealed no unambiguous preference for V3+, although simple bond-length calculation suggests the preference of the M3 site. However, it is quite straightforward that the M1,2 site is better suitable for V4+. If the possible octahedral distortion is considered, the M1,2O6 octahedron is subject to a smaller change in distortion if occupied by V3+ than the M3O6 octahedron. Consequently, considering the results of both the crystal field Superposition Model and Bond-Valence Model calculations, we assume that both V3+ and V4+ prefer the M1,2 site.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10504 - Mineralogy

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2023

Kód důvěrnosti údajů

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

Název periodika

Mineralogical Magazine

ISSN

0026-461X

e-ISSN

1471-8022

Svazek periodika

87

Číslo periodika v rámci svazku

4

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

12

Strana od-do

599-610

Kód UT WoS článku

001032815400001

EID výsledku v databázi Scopus

2-s2.0-85164327299