Simulation studies on the pyrope-grossular garnet solid solution

Bosenick, Anne; Dove, MT; Geiger, Charles A.

doi:10.1007/s002690000088

Cited by 74 publications

(57 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The lowest temperature of decomposition was observed in the case of the garnet with a composition close to almandine, which could be explained in terms of the induced iron reduction. In contrast, the garnet with a composition close to pyrope, presents not only Fe 3+ and Cr 3+ in the octahedral sites, but also Ca 2+ in the dodecahedral sites, which might increase the instability of the lattice at high temperatures [24,25]. The ferric ions reduce to ferrous ions, but, apparently, they do not stay in the same octahedral site as there was no evidence in the Mössbauer spectra, where it is not possible to ascribe any doublet to Fe 2+ in the octahedral site.…”

Section: Variation Of Onset Temperature With Respect To the Fe Contenmentioning

confidence: 95%

The influence of the iron content on the reductive decomposition of A3−xFexAl2Si3O12 garnets (A = Mg, Mn; 0.47 ≤ x ≤ 2.85)

Aparicio¹,

Filip²,

Mashlan³

et al. 2014

AIP Conference Proceedings

View full text Add to dashboard Cite

Abstract. Thermally-induced reductive decomposition of natural iron-bearing garnets of the almandine-pyrope and almandine-spessartine series were studied at temperatures up to 1200 °C (heating rate of 10 °C/min) under atmosphere of forming gas (10% of H 2 in N 2 ). Crystallochemical formula of the studied garnet was calculated as VIII (A 3-x Fe 2+x ) VI (Al, Fe 3+ ) 2 Si 3 O 12 , where the amount of Fe 3+ in the octahedral sites is negligible with the exception of pyrope, A = Mg, Mn, and 0.47 x 2.85. The observed decomposition temperature, determined from differential scanning calorimetry and thermogravimetry, is greater than 1000 °C in all cases and showed almost linear dependence on the iron content in the dodecahedral sites of the studied garnets, with the exception of garnet with a near-pyrope composition (Prp 80 Alm 20 ). The initial garnet samples and decomposition products were characterized in details by means of X-ray powder diffraction and 57 Fe Mössbauer spectroscopy. We found that all studied garnets have common decomposition products such as metallic iron (in general, rounded particles below 4 μm) and Fe-spinel; the other identified decomposition products depend on starting chemical composition of the garnet: Fe-cordierite, olivine (fayalite or tephroite), cristobalite, pyroxene (enstatite or pigeonite), and anorthite. Anorthite and pigeonite were only present in garnets with Ca in the dodecahedral site. All the identified phases were usually well crystallized.

show abstract

Section: Variation Of Onset Temperature With Respect To the Fe Contenmentioning

confidence: 95%

The influence of the iron content on the reductive decomposition of A3−xFexAl2Si3O12 garnets (A = Mg, Mn; 0.47 ≤ x ≤ 2.85)

Aparicio¹,

Filip²,

Mashlan³

et al. 2014

AIP Conference Proceedings

View full text Add to dashboard Cite

show abstract

“…It is known that at least one of the repulsion poten tial parameters (А) depends on the charge state of interacting ions [22][23][24]; therefore, we searched for the combinations of BMH potential parameters that would satisfy the check criteria for the second of the charge sets and would not contradict the known infor mation. One of these combinations is given in the table.…”

Section: Relaxation Of the Batio 3 Crystal Structure In The Vicinity mentioning

confidence: 99%

Simulation of the OH− group location in the cubic phase of BaTiO3 crystals

Yatsenko

2012

Crystallogr. Rep.

View full text Add to dashboard Cite

show abstract

“…This formula has been employed extensively in many recent studies of order/disorder and mixing phenomena in minerals. [14][15][16][17][18][19][20][21][22][23][24]29,30 The J's were calculated with the leastsquares method from the static lattice energies and f AB͑n͒ numbers of a large set of supercell structures. Equation ͑4͒ was subsequently used to calculate temperature-dependent mixing properties with the Monte Carlo method.…”

Section: Expansion Of the Excess Enthalpymentioning

confidence: 99%

“…For example, in grossular pyrope garnet, Ca 3 Al 2 Si 3 O 12 -Mg 3 Al 2 Si 3 O 12 , Ca and Mg are mixed over 24 out of the total number of 160 sites. 14 In such a case the approach based on ordered structures offers little advantage because the ordering affects just a small part of the structure and cannot significantly reduce the supercell size. At the same time, when interactions between exchangeable atoms in minerals are mediated by the "extra" elements, the role of many-body cluster interactions is likely to be small.…”

Section: Introductionmentioning

confidence: 99%

“…At the same time, when interactions between exchangeable atoms in minerals are mediated by the "extra" elements, the role of many-body cluster interactions is likely to be small. The majority of the recent studies concerned with order/disorder and mixing phenomena in minerals [14][15][16][17][18][19][20][21][22][23][24] have therefore considered pairwise ECIs only. Since in large supercells a large number of different pair ECIs can be included in the expansion, it was usually possible to achieve reasonably accurate fits to the excess enthalpies of the sampled structures.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Subsolidus phase relations in theCaCO3–MgCO3system predicted from the excess enthalpies of supercell structures with single and double defects

2009

View full text Add to dashboard Cite

The thermodynamic mixing properties of a binary ͑A x B 1−x ͒R solid solution are evaluated from the enthalpies of supercell structures A m−2 B 2 R m and B m−2 A 2 R m , where m is the number of the exchangeable sites in the supercell. The excess enthalpies of these structures are converted into concentration-dependent pairwise effective cluster interactions J n , i.e., the enthalpies of the intracrystalline reactions AA+ BB 2AB acting at the n-neighbor distance within the supercell. The pairwise interactions calculated in this way for all possible distances within 3 ϫ 3 ϫ 1 supercells of R3c calcite and magnesite ͑m =54͒ are combined to form an effective Ising-type Hamiltonian from which temperature-dependent enthalpies, entropies, and free energies of mixing are evaluated with the Monte Carlo method. The calculated phase diagram with two miscibility gaps separated by a field of stability of the R3 dolomite phase is in good agreement with available experimental data, thereby showing that the existence of the intermediate ordered compound can be predicted from the analysis of the supercell structures whose compositions approach the diluted limits.

show abstract

Simulation studies on the pyrope-grossular garnet solid solution

Cited by 74 publications

References 0 publications

The influence of the iron content on the reductive decomposition of A3−xFexAl2Si3O12 garnets (A = Mg, Mn; 0.47 ≤ x ≤ 2.85)

The influence of the iron content on the reductive decomposition of A3−xFexAl2Si3O12 garnets (A = Mg, Mn; 0.47 ≤ x ≤ 2.85)

Simulation of the OH− group location in the cubic phase of BaTiO3 crystals

Subsolidus phase relations in theCaCO3–MgCO3system predicted from the excess enthalpies of supercell structures with single and double defects

Contact Info

Product

Resources

About