Rationalization of the crystal structure of eudidymite in the light of the Extended Zintl-Klemm Concept

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Marco E. Ciriotti
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Rationalization of the crystal structure of eudidymite in the light of the Extended Zintl-Klemm Concept

Messaggio da Marco E. Ciriotti » sab 30 nov, 2019 16:42

Prossima pubblicazione.

Referenza:
▪ Vegas, A. & Jenkins, H.D.B. (2020): Rationalization of the crystal structure of Eudidymite Na2Be2[Si[4]6O15]·H2O in the light of the Extended Zintl-Klemm Concept. Its similarity with the structure of (NH4)2Ge[6][Ge[4]6O15]. Acta Crystallographica, B76, (in press).

Synopsis:
The structure of the mineral eudidymite (Na2Be2[Si[4]6O15]·H2O) is re-interpreted on the basis of the Extended Zintl-Klemm Concept. The donor atoms (Na, Be) convert the Si atoms into pseudo-P which form a three-connected Si-skeleton, characteristic of pentels (Group 15 elements). These skeletons are connected by fragments of the β-BeO structure. The [Si[4]6O15] substructure is identical to the [Ge[4]6O15] groups (Ge[4] atoms error Ψ-As) in (NH4)2Ge[6][Ge[4]6O15], in spite of their quite different compositions.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
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Re: Rationalization of the crystal structure of eudidymite in the light of the Extended Zintl-Klemm Concept

Messaggio da Marco E. Ciriotti » sab 30 nov, 2019 20:36

Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 26364
Iscritto il: ven 25 giu, 2004 11:31
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Re: Rationalization of the crystal structure of eudidymite in the light of the Extended Zintl-Klemm Concept

Messaggio da Marco E. Ciriotti » mer 15 gen, 2020 19:32

Referenza:
▪ Vegas, A. & Jenkins, H.D.B. (2020): Rationalization of the crystal structure of Eudidymite Na2Be2[Si[4]6O15]·H2O in the light of the Extended Zintl-Klemm Concept. Its similarity with the structure of (NH4)2Ge[6][Ge[4]6O15]. Acta Crystallographica, B76, (in press).

Abstract:
The structure of eudidymite is described in light of the extended Zintl–Klemm concept which considers that Na and Be atoms transfer their six valence electrons to the six Si atoms, converting them into Ψ‐P which forms a skeleton characteristic of pentels (Group 15 elements) and is similar to that described in the compound (NH4)2Ge[6][Ge[4]6O15] when analysed in the same manner. The Si[4] skeleton is formed of bilayers that are connected through Be2O6 groups which are in fact fragments of the β‐BeO structure which bridge the two contiguous Si‐bilayers by sharing O atoms. In this context, the Be atoms play a dual role, i.e. on the one hand converting the Si atoms into Ψ‐P, on the other hand replicating fragments of its own β‐BeO structure. The Be atoms partially reproduce their own structure despite it being enclosed in a more complex network such as in Na2Be2[Si[4]6O15]·H2O. Calculations of the ionic strength I considering Si as Ψ‐P is energetically more favourable than when I is calculated on the basis of tetravalent Si in the silicate, justifying this new approach of developing the theory of pseudo‐structure generation. This approach offers a major new development in the study of crystal structures.
Marco E. Ciriotti

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