Twinning of aragonite - the OD approach

Emil Makovicky

doi:10.1007/s00710-012-0219-5

Twinning of aragonite - the OD approach

Emil Makovicky

Geologi

7 Citationer (Scopus)

Abstract

Twinning process in aragonite and its isotypes on (110) may be described by OD (order -disorder) mechanism. In the Pmcn orientation of aragonite, the OD layer has layer group P(c)mb, with the direction perpendicular to the layer indicated by parentheses. The lattice parameters of the OD layer are b 9.39 Å (the [110] diagonal of the aragonite lattice) and c 5.74 Å, its thickness a is d(110) of the aragonite lattice, equal to 4. 21 Å. The interlayer σ-PO's are {(2_2/n1/2,1)2_-1/2/a₂2₁/n_2,-1/2}, brackets denote the direction perpendicular to the OD layer. Two polytypes with maximum degree of order can be derived. MDO1 is Pmcn aragonite itself, MDO2 is a Pcab polytype with a 8.42 Å, b 9.39 Å and c 5.74 Å, unknown as an independent structure. Desymmetrization of the aragonite structure appears to limit occurrence of the MDO2 principle to occasional twin boundaries.

Originalsprog	Engelsk
Tidsskrift	Mineralogy and Petrology
Vol/bind	106
Udgave nummer	1-2
Sider (fra-til)	19-24
Antal sider	6
ISSN	0930-0708
DOI	https://doi.org/10.1007/s00710-012-0219-5
Status	Udgivet - sep. 2012

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10.1007/s00710-012-0219-5

Citationsformater

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title = "Twinning of aragonite - the OD approach",

abstract = "Twinning process in aragonite and its isotypes on (110) may be described by OD (order -disorder) mechanism. In the Pmcn orientation of aragonite, the OD layer has layer group P(c)mb, with the direction perpendicular to the layer indicated by parentheses. The lattice parameters of the OD layer are b 9.39 {\AA} (the [110] diagonal of the aragonite lattice) and c 5.74 {\AA}, its thickness a is d(110) of the aragonite lattice, equal to 4. 21 {\AA}. The interlayer σ-PO's are {(22/n1/2,1)2-1/2/a221/n2,-1/2}, brackets denote the direction perpendicular to the OD layer. Two polytypes with maximum degree of order can be derived. MDO1 is Pmcn aragonite itself, MDO2 is a Pcab polytype with a 8.42 {\AA}, b 9.39 {\AA} and c 5.74 {\AA}, unknown as an independent structure. Desymmetrization of the aragonite structure appears to limit occurrence of the MDO2 principle to occasional twin boundaries.",

author = "Emil Makovicky",

year = "2012",

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doi = "10.1007/s00710-012-0219-5",

language = "English",

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journal = "Mineralogy and Petrology",

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AU - Makovicky, Emil

PY - 2012/9

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N2 - Twinning process in aragonite and its isotypes on (110) may be described by OD (order -disorder) mechanism. In the Pmcn orientation of aragonite, the OD layer has layer group P(c)mb, with the direction perpendicular to the layer indicated by parentheses. The lattice parameters of the OD layer are b 9.39 Å (the [110] diagonal of the aragonite lattice) and c 5.74 Å, its thickness a is d(110) of the aragonite lattice, equal to 4. 21 Å. The interlayer σ-PO's are {(22/n1/2,1)2-1/2/a221/n2,-1/2}, brackets denote the direction perpendicular to the OD layer. Two polytypes with maximum degree of order can be derived. MDO1 is Pmcn aragonite itself, MDO2 is a Pcab polytype with a 8.42 Å, b 9.39 Å and c 5.74 Å, unknown as an independent structure. Desymmetrization of the aragonite structure appears to limit occurrence of the MDO2 principle to occasional twin boundaries.

AB - Twinning process in aragonite and its isotypes on (110) may be described by OD (order -disorder) mechanism. In the Pmcn orientation of aragonite, the OD layer has layer group P(c)mb, with the direction perpendicular to the layer indicated by parentheses. The lattice parameters of the OD layer are b 9.39 Å (the [110] diagonal of the aragonite lattice) and c 5.74 Å, its thickness a is d(110) of the aragonite lattice, equal to 4. 21 Å. The interlayer σ-PO's are {(22/n1/2,1)2-1/2/a221/n2,-1/2}, brackets denote the direction perpendicular to the OD layer. Two polytypes with maximum degree of order can be derived. MDO1 is Pmcn aragonite itself, MDO2 is a Pcab polytype with a 8.42 Å, b 9.39 Å and c 5.74 Å, unknown as an independent structure. Desymmetrization of the aragonite structure appears to limit occurrence of the MDO2 principle to occasional twin boundaries.

U2 - 10.1007/s00710-012-0219-5

DO - 10.1007/s00710-012-0219-5

M3 - Journal article

SN - 0930-0708

VL - 106

SP - 19

EP - 24

JO - Mineralogy and Petrology

JF - Mineralogy and Petrology

IS - 1-2

ER -

Twinning of aragonite - the OD approach

Abstract

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