caa a22 4500 378923404 CHVBK 20180305123611.0 cr unu---uuuuu 161128e20040501xx s 000 0 eng 10.1524/zkri.219.5.272.32743 doi (NATIONALLICENCE)gruyter-10.1524/zkri.219.5.272.32743 Local mean chromium-oxygen distances in Cr3+-centered octahedra of natural grossular-uvarovite garnet solid solutions from electronic absorption spectra [Elektronische Daten] [Klaus Langer, Alexej N. Platonov, Stanislav S. Matsyuk] The crystal field parameter 10Dq[cm⁻¹] of octahedral chromium obtained as the energy of the 4A2g → 4T2g band of Cr3+ in the electronic absorption spectra, EAS, of a series of 13 natural grossular-uvarovite garnets with compositions close to the binary join Ca3(Al1-xCrx)2Si3O12, depend on the chromium fraction xCr of the solid solutions as 10Dq[cm⁻¹] = (-515.51 · xCr) + 16579 (r = 0.984) The 10Dq[cm⁻¹]-values were evaluated in terms of local mean octahedral distances, R̅(Cr-O), [Å]local with the result that R̅ (Cr-O) local = 0.01262 · xCr + 1.9812 (r = 0.982) (a) Equation (a) is in very good agreement with mean 〈Al/Cr—O〉; distances of "individual” octahedra R̅i calculated for the case XCr(individual) = 1.00 from the distance relations obtained in X-ray structure refinements of low symmetry chromian garnets (Wildner and Andrut, 2001). The proves again, that the EAS-method to derive local 3dN-ion-oxygen distances is reliable. R̅ (Cr-O) local = ƒ(xCr) and the corresponding R̅i-function deviate strongly from the Vegard line of the crystal averaged function R̅(Cr-O)average = ƒ(xCr), the "virtual crystal model”. This indicates significant structural relaxation around Cr3+[6] in the garnet solid solutions studied. The relaxation coefficient calculated from the data, ∊lim xCr→0 = 0.82, is closer to ∊ = 1.0 for full relaxation, i.e. the "hard sphere model”, than to ∊ = 0.0 for absent relaxation in the "virtual crystal” model. This is proposedly related to the uptake of strain around octahedral chromium, in the large (CaO8) polyhedra interconnected with the octahedra of the grossular-uvarovite garnets. © 2004 Oldenbourg Wissenschaftsverlag GmbH Crystallography nationallicence Inorganic chemistry nationallicence Organic chemistry nationallicence Langer Klaus aut Platonov Alexej N. aut Matsyuk Stanislav S. aut Zeitschrift für Kristallographie - Crystalline Materials De Gruyter Oldenbourg 219/5(2004-05-01), 272-277 2194-4946 219:5<272 2004 219 zkri https://doi.org/10.1524/zkri.219.5.272.32743 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1524/zkri.219.5.272.32743 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Langer Klaus aut NATIONALLICENCE 700 1- Platonov Alexej N. aut NATIONALLICENCE 700 1- Matsyuk Stanislav S. aut NATIONALLICENCE 773 0- Zeitschrift für Kristallographie - Crystalline Materials De Gruyter Oldenbourg 219/5(2004-05-01), 272-277 2194-4946 219:5<272 2004 219 zkri CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter