http://www.cnr.it/ontology/cnr/individuo/prodotto/ID292844
Ab-initio investigation of the thermodynamic stability of the magnesio-wüstite solid solution under Earth's lower mantle conditions (Abstract/Poster in atti di convegno)
- Type
- Label
- Ab-initio investigation of the thermodynamic stability of the magnesio-wüstite solid solution under Earth's lower mantle conditions (Abstract/Poster in atti di convegno) (literal)
- Anno
- 2014-01-01T00:00:00+01:00 (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
- 10.3301/ROL.2014.140 (literal)
- Alternative label
Merli M
Sciascia L
Pavese A
Diella V (2014)
Ab-initio investigation of the thermodynamic stability of the magnesio-wüstite solid solution under Earth's lower mantle conditions
in 87° Congresso della Società Geologica Italiana e 90° Congresso della Società Italiana di Mineralogia e Petrologia, Milano, 10-12 09 2014
(literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- Merli M
Sciascia L
Pavese A
Diella V (literal)
- Pagina inizio
- Pagina fine
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#titoloVolume
- The Future of the Italian Geosciences - The Italian Geosciences of the Future (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
- Rivista
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#pagineTotali
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroFascicolo
- Note
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
- Dipartimento di Scienze della Terra e del Mare- Università degli Studi di Palermo
Dipartimento di Scienze della Terra e del Mare- Università degli Studi di Palermo
Dipartimento Scienze della Terra ''A. Desio'', Università degli Studi di Milano
Consiglio Nazionale delle Ricerche, CNR-IDPA, Sezione di Milano (literal)
- Titolo
- Ab-initio investigation of the thermodynamic stability of the magnesio-wüstite solid solution under Earth's lower mantle conditions (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#curatoriVolume
- B. Cesare, E. Erba, B. Carmina, L. Fascio, F.M. Petti, A. Zuccari (literal)
- Abstract
- Mg-wüstite, (Mg,Fe)O, is the second most abundant phase in the Earth's lower mantle. A profound understanding of
the thermodynamic stability of this phase under deep mantle conditions is thus crucial for developing accurate models
of the Earth's interior and the importance of drawing a complete picture of the stability fields of the Mg-wustite solid
solution, especially at high pressure/temperature regimes, is straightforward.
In the light of the above considerations, the present work has been undertaken where the thermo-chemical properties
of the (Mg,Fe)O solid solution, over a wide PT range, have been modelled using mixing Helmholtz energy,
?F T, x mixing. Calculations have been performed by means of cluster expansion, quantum mechanical and semiempirical
techniques.
Both high-spin (HS) and low-spin (LS) configurations of iron have been explored as a function of composition (x:
molar fraction of FeO) over the MgO-FeO binary. Only the HS-model provides physically sound results at room
pressure, yielding a correct trend of cell edge versus composition, whereas LS's issues are at variance with
observations. Mixing Helmholtz energy has been parametrized by the following relationship ?F T, x mixing =
x×y×[(U T ! + U T ! × x - y + U T ! ± (x - y)!, where y = 1 - x and U!(T) are polynomials in T of the third
order. ?F T, x mixing exhibits a quasi-symmetric behaviour and allows one to build the T-X phase relations diagram
over the MgO-FeO join. On the basis of the HS-model including vibrational contribution to Helmholtz energy, a solid
solution's critical temperature of some 950 K has been predicted, remarkably lower than olivine's and Mg-Fe-garnet's.
All this points to a more difficult Mg-Fe mixing in periclase-like structure than olivine and garnet, which, in turn,
provide more degrees of freedom for atomic relaxation. From ?F T, x mixing, the values of ?H T, x mixing and
?S T, x mixing have been derived, both exhibiting so modest a dependence on T as to be negligible.
?H T, x mixing and ?S T, x mixing exhibit quasi-regularity; either has been parametrized as W×x×(1 - x),
obtaining W!,!\"!!\" and W!,!\"!!\" of 17.7 kJ/mol and 26.8 J/mol/K, respectively. ?S T, x excess has been estimated to
be smaller than 0.5 J/mol/K in absolute Moreover, it has been observed that the HS-configuration is stable and promote
Mg-Fe solid solution up to >>15 GPa better than LS does. At higher pressures, the LS-model becomes favourite and
increasingly stabilizes (Mg,Fe)O upon rising P, whereas HS predicts ex-solving into the end members above >>40 GPa (literal)
- Prodotto di
- Autore CNR
- Insieme di parole chiave
Incoming links:
- Prodotto
- Autore CNR di
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#rivistaDi
- Insieme di parole chiave di