Effect of Rattling on the Interatomic Interaction in Oxide Spinels MgAl2O4 and ZnGa2O4

Sinha, M.M.; Sinch, N. P.; Prasad, Kamlesh; Gupta, H.C.

doi:10.1002/pssb.2221900232

Cited by 9 publications

(3 citation statements)

References 10 publications

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“…This is the expected behavior, and it is in correlation with the zero pressure bond distance values ͑see 20 the compression in these direct spinels is ''achieved mostly by deformation of the tetrahedra.'' In contrast, Sinha et al 21 predicted greater force constants for the divalent-oxygen bonds than for the trivalent-oxygen ones in MgAl 2 O 4 and ZnGa 2 O 4 , after a parametrization of Raman spectrum data. Although a rattling behavior for trivalent cations may be suggested in the direct spinel structures, our results clearly illustrate the dominant role of trivalent cationoxygen bonds in the compressibility of these compounds.…”

Section: Bond Polyhedral and Macroscopic Compressibilitiesmentioning

confidence: 88%

Theoretical explanation of the uniform compressibility behavior observed in oxide spinels

et al. 2001

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Simple algebraic equations show that the bulk compressibility in spinel-type compounds can be expressed by means of cation oxide polyhedral compressibilities and a term that accounts for the pressure effect on the internal oxygen position in the unit cell. The equations explain ͑i͒ the difference of compressibilities at octahedral and tetrahedral sites, ͑ii͒ why the macroscopic bulk modulus can be estimated as the average of these polyhedral bulk moduli, and ͑iii͒ the uniform behavior found in oxide spinels under hydrostatic pressure. Quantum-mechanical ab initio perturbed ion results on MgAl 2 O 4 , ZnAl 2 O 4 , ZnGa 2 O 4 , and MgGa 2 O 4 direct spinels and on MgGa 2 O 4 inverse spinel are reported to illustrate the interpretative capabilities of the proposed equations.

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Section: Bond Polyhedral and Macroscopic Compressibilitiesmentioning

confidence: 88%

Theoretical explanation of the uniform compressibility behavior observed in oxide spinels

et al. 2001

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“…Five Raman-active fundamental vibrations, A 1g + E g + 3T 2g , are predicted [78]. Theoretical calculations yield the A 1g at~762 cm −1 , E g at~408 cm −1 , and T 2g at~667 cm −1 (T 2g (2) ),~557 cm −1 (T 2g(3) ) and~317 cm −1 (T 2g (1) ; [79][80][81][82][83][84][85]). The intensity of these Raman modes decreases in the order of E g > T 2g(2) > A 1g > T 2g (1) > T 2g (3) [83].…”

Section: Raman Features Of Nearly Normal Mgal 2 O 4 -Spmentioning

confidence: 93%

Si-Disordering in MgAl2O4-Spinel under High P-T Conditions, with Implications for Si-Mg Disorder in Mg2SiO4-Ringwoodite

Liu

Bao

et al. 2018

Minerals

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A series of Si-bearing MgAl 2 O 4 -spinels were synthesized at 1500-1650 • C and 3-6 GPa. These spinels had SiO 2 contents of up to~1.03 wt % and showed a substitution mechanism of Si 4+ + Mg 2+ = 2Al 3+ . Unpolarized Raman spectra were collected from polished single grains, and displayed a set of well-defined Raman peaks at~610, 823, 856 and 968 cm −1 that had not been observed before. Aided by the Raman features of natural Si-free MgAl 2 O 4 -spinel, synthetic Si-free MgAl 2 O 4 -spinel, natural low quartz, synthetic coesite, synthetic stishovite and synthetic forsterite, we infer that these Raman peaks should belong to the SiO 4 groups. The relations between the Raman intensities and SiO 2 contents of the Si-bearing MgAl 2 O 4 -spinels suggest that under some P-T conditions, some Si must adopt the M-site. Unlike the SiO 4 groups with very intense Raman signals, the SiO 6 groups are largely Raman-inactive. We further found that the Si cations primarily appear on the T-site at P-T conditions ≤~3-4 GPa and 1500 • C, but attain a random distribution between the T-site and M-site at P-T conditions ≥~5-6 GPa and 1630-1650 • C. This Si-disordering process observed for the Si-bearing MgAl 2 O 4 -spinels suggests that similar Si-disordering might happen to the (Mg,Fe) 2 SiO 4 -spinels (ringwoodite), the major phase in the lower part of the mantle transition zone of the Earth and the benchmark mineral for the very strong shock stage experienced by extraterrestrial materials. The likely consequences have been explored.

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“…cm -1 , and T2g at ~667 cm -1 (T2g(2)), ~557 cm -1 (T2g(3)) and ~317 cm -1 (T2g(1); [79][80][81][82][83][84][85]). The intensity of these Raman modes decreases in the order of Eg > T2g(2) > A1g > T2g(1) > T2g(3) [83].…”

Section: Raman Features Of Nearly Normal Mgal2o4-spmentioning

confidence: 99%

Si-Disordering in MgAl2O4-Spinel at High P-T Conditions, with Implication to Si-Mg Disorder in Mg2SiO4-Ringwoodite

Liu¹,

Liu²,

Bao³

et al. 2018

Preprint

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A series of Si-bearing MgAl2O4-spinels were synthesized at 1500-1650 °C and 3–6 GPa. These spinels had SiO2 contents up to ~1.03 wt%, and showed a substitution mechanism of Si4+ + Mg2+ = 2Al3+. Unpolarized Raman spectra were collected from polished single grains, and displayed a set of well-defined Raman peaks at ~610, 823, 856 and 968 cm-1 which had not been observed before. Aided with the Raman features of natural Si-free MgAl2O4-spinel, synthetic Si-free MgAl2O4-spinel, natural low quartz, synthetic coesite, synthetic stishovite and synthetic forsterite, we infer that these Raman peaks should belong to the SiO4 groups. The relations between the Raman intensities and SiO2 contents of the Si-bearing MgAl2O4-spinels suggest that at some P-T conditions some Si must adopt the M-site. Unlike the SiO4 groups with very intense Raman signals, the SiO6 groups are largely Raman-inactive. We have further found that the Si cations primarily appear on the T-site at P-T conditions ≤ ~3–4 GPa and 1500 °C, but attain a random distribution between the T-site and M-site at P-T conditions ≥ ~5–6 GPa and 1630–1650 °C. This Si-disordering process observed for the Si-bearing MgAl2O4-spinels hints that similar Si-disordering might happen to the (Mg,Fe)2SiO4-spinels (ringwoodite), the major phase in the lower part of the mantle transition zone of the Earth and the index mineral for the very strong shock stage experienced by extraterrestrial materials. The likely consequences have been explored.

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Effect of Rattling on the Interatomic Interaction in Oxide Spinels MgAl₂O₄ and ZnGa₂O₄

Cited by 9 publications

References 10 publications

Theoretical explanation of the uniform compressibility behavior observed in oxide spinels

Theoretical explanation of the uniform compressibility behavior observed in oxide spinels

Si-Disordering in MgAl2O4-Spinel under High P-T Conditions, with Implications for Si-Mg Disorder in Mg2SiO4-Ringwoodite

Si-Disordering in MgAl<sub>2</sub>O<sub>4</sub>-Spinel at High <em>P</em>-<em>T</em> Conditions, with Implication to Si-Mg Disorder in Mg<sub>2</sub>SiO<sub>4</sub>-Ringwoodite

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