Dmisteinbergite, CaAl2Si2O8, a metastable polymorph of anorthite: Crystal-structure and raman spectroscopic study of the holotype specimen

Andrey A. Zolotarev, Sergey V. Krivovichev, Taras L. Panikorovskii, Vladislav V. Gurzhiy, Vladimir N. Bocharov, Mikhail A. Rassomakhin

Research output

Abstract

The crystal structure of dmisteinbergite has been determined using crystals from the type locality in Kopeisk city, Chelyabinsk area, Southern Urals, Russia. The mineral is trigonal, with the following structure: P312, a = 5.1123(2), c = 14.7420(7) Å, V = 333.67(3) Å3, R1 = 0.045, for 762 unique observed reflections. The most intense bands of the Raman spectra at 327s, 439s, 892s, and 912s cm-1 correspond to different types of tetrahedral stretching vibrations: Si-O, Al-O, O-Si-O, and O-Al- O. The weak bands at 487w, 503w, and 801w cm-1 can be attributed to the valence and deformation modes of Si-O and Al-O bond vibrations in tetrahedra. The weak bands in the range of 70-200 cm-1 can be attributed to Ca-O bond vibrations or lattice modes. The crystal structure of dmisteinbergite is based upon double layers of six-membered rings of corner-sharing AlO4 and SiO4 tetrahedra. The obtained model shows an ordering of Al and Si over four distinct crystallographic sites with tetrahedral coordination, which is evident from the average <T-O> bond lengths (T = Al, Si), equal to 1.666, 1.713, 1.611, and 1.748 Å for T1, T2, T3, and T4, respectively. One of the oxygen sites (O4) is split, suggesting the existence of two possible conformations of the [Al2Si2O8]2- layers, with different systems of ditrigonal distortions in the adjacent single layers. The observed disorder has a direct influence upon the geometry of the interlayer space and the coordination of the Ca2 site. Whereas the coordination of the Ca1 site is not influenced by the disorder and is trigonal antiprismatic (distorted octahedral), the coordination environment of the Ca2 site includes disordered O atoms and is either trigonal prismatic or trigonal antiprismatic. The observed structural features suggest the possible existence of different varieties of dmisteinbergite that may differ in: (i) degree of disorder of the Al/Si tetrahedral sites, with completely disordered structure having the P63/mcm symmetry; (ii) degree of disorder of the O sites, which may have a direct influence on the coordination features of the Ca2+ cations; (iii) polytypic variations (different stacking sequences and layer shifts). The formation of dmisteinbergite is usually associated with metastable crystallization in both natural and synthetic systems, indicating the kinetic nature of this phase. Information-based complexity calculations indicate that the crystal structures of metastable CaAl2Si2O8 polymorphs dmisteinbergite and svyatoslavite are structurally and topologically simpler than that of their stable counterpart, anorthite, which is in good agreement with Goldsmith’s simplexity principle and similar previous observations.

Original languageEnglish
Article number570
JournalMinerals
Volume9
Issue number10
Early online date20 Sep 2019
DOIs
Publication statusPublished - Oct 2019

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anorthite
Polymorphism
crystal structure
Crystal structure
vibration
Chemical bonds
Bond length
Crystal lattices
Stretching
Conformations
Raman scattering
Minerals
Crystallization
Positive ions
type locality
Atoms
Crystals
Kinetics
Oxygen
Geometry

Scopus subject areas

  • Geotechnical Engineering and Engineering Geology
  • Geology

Cite this

@article{c61980f0ea21471293b30a0e478137e5,
title = "Dmisteinbergite, CaAl2Si2O8, a metastable polymorph of anorthite: Crystal-structure and raman spectroscopic study of the holotype specimen",
abstract = "The crystal structure of dmisteinbergite has been determined using crystals from the type locality in Kopeisk city, Chelyabinsk area, Southern Urals, Russia. The mineral is trigonal, with the following structure: P312, a = 5.1123(2), c = 14.7420(7) {\AA}, V = 333.67(3) {\AA}3, R1 = 0.045, for 762 unique observed reflections. The most intense bands of the Raman spectra at 327s, 439s, 892s, and 912s cm-1 correspond to different types of tetrahedral stretching vibrations: Si-O, Al-O, O-Si-O, and O-Al- O. The weak bands at 487w, 503w, and 801w cm-1 can be attributed to the valence and deformation modes of Si-O and Al-O bond vibrations in tetrahedra. The weak bands in the range of 70-200 cm-1 can be attributed to Ca-O bond vibrations or lattice modes. The crystal structure of dmisteinbergite is based upon double layers of six-membered rings of corner-sharing AlO4 and SiO4 tetrahedra. The obtained model shows an ordering of Al and Si over four distinct crystallographic sites with tetrahedral coordination, which is evident from the average <T-O> bond lengths (T = Al, Si), equal to 1.666, 1.713, 1.611, and 1.748 {\AA} for T1, T2, T3, and T4, respectively. One of the oxygen sites (O4) is split, suggesting the existence of two possible conformations of the [Al2Si2O8]2- layers, with different systems of ditrigonal distortions in the adjacent single layers. The observed disorder has a direct influence upon the geometry of the interlayer space and the coordination of the Ca2 site. Whereas the coordination of the Ca1 site is not influenced by the disorder and is trigonal antiprismatic (distorted octahedral), the coordination environment of the Ca2 site includes disordered O atoms and is either trigonal prismatic or trigonal antiprismatic. The observed structural features suggest the possible existence of different varieties of dmisteinbergite that may differ in: (i) degree of disorder of the Al/Si tetrahedral sites, with completely disordered structure having the P63/mcm symmetry; (ii) degree of disorder of the O sites, which may have a direct influence on the coordination features of the Ca2+ cations; (iii) polytypic variations (different stacking sequences and layer shifts). The formation of dmisteinbergite is usually associated with metastable crystallization in both natural and synthetic systems, indicating the kinetic nature of this phase. Information-based complexity calculations indicate that the crystal structures of metastable CaAl2Si2O8 polymorphs dmisteinbergite and svyatoslavite are structurally and topologically simpler than that of their stable counterpart, anorthite, which is in good agreement with Goldsmith’s simplexity principle and similar previous observations.",
keywords = "Burned coal dumps, Crystal structure, Dmisteinbergite, Feldspar, Kopeisk, Metastability, Polymorphism, Raman spectroscopy, Ural region",
author = "Zolotarev, {Andrey A.} and Krivovichev, {Sergey V.} and Panikorovskii, {Taras L.} and Gurzhiy, {Vladislav V.} and Bocharov, {Vladimir N.} and Rassomakhin, {Mikhail A.}",
note = "Zolotarev, A.A.; Krivovichev, S.V.; Panikorovskii, T.L.; Gurzhiy, V.V.; Bocharov, V.N.; Rassomakhin, M.A. Dmisteinbergite, CaAl2Si2O8, a Metastable Polymorph of Anorthite: Crystal-Structure and Raman Spectroscopic Study of the Holotype Specimen. Minerals 2019, 9, 570.",
year = "2019",
month = "10",
doi = "10.3390/min9100570",
language = "English",
volume = "9",
journal = "Minerals",
issn = "2075-163X",
publisher = "MDPI AG",
number = "10",

}

TY - JOUR

T1 - Dmisteinbergite, CaAl2Si2O8, a metastable polymorph of anorthite

T2 - Crystal-structure and raman spectroscopic study of the holotype specimen

AU - Zolotarev, Andrey A.

AU - Krivovichev, Sergey V.

AU - Panikorovskii, Taras L.

AU - Gurzhiy, Vladislav V.

AU - Bocharov, Vladimir N.

AU - Rassomakhin, Mikhail A.

N1 - Zolotarev, A.A.; Krivovichev, S.V.; Panikorovskii, T.L.; Gurzhiy, V.V.; Bocharov, V.N.; Rassomakhin, M.A. Dmisteinbergite, CaAl2Si2O8, a Metastable Polymorph of Anorthite: Crystal-Structure and Raman Spectroscopic Study of the Holotype Specimen. Minerals 2019, 9, 570.

PY - 2019/10

Y1 - 2019/10

N2 - The crystal structure of dmisteinbergite has been determined using crystals from the type locality in Kopeisk city, Chelyabinsk area, Southern Urals, Russia. The mineral is trigonal, with the following structure: P312, a = 5.1123(2), c = 14.7420(7) Å, V = 333.67(3) Å3, R1 = 0.045, for 762 unique observed reflections. The most intense bands of the Raman spectra at 327s, 439s, 892s, and 912s cm-1 correspond to different types of tetrahedral stretching vibrations: Si-O, Al-O, O-Si-O, and O-Al- O. The weak bands at 487w, 503w, and 801w cm-1 can be attributed to the valence and deformation modes of Si-O and Al-O bond vibrations in tetrahedra. The weak bands in the range of 70-200 cm-1 can be attributed to Ca-O bond vibrations or lattice modes. The crystal structure of dmisteinbergite is based upon double layers of six-membered rings of corner-sharing AlO4 and SiO4 tetrahedra. The obtained model shows an ordering of Al and Si over four distinct crystallographic sites with tetrahedral coordination, which is evident from the average <T-O> bond lengths (T = Al, Si), equal to 1.666, 1.713, 1.611, and 1.748 Å for T1, T2, T3, and T4, respectively. One of the oxygen sites (O4) is split, suggesting the existence of two possible conformations of the [Al2Si2O8]2- layers, with different systems of ditrigonal distortions in the adjacent single layers. The observed disorder has a direct influence upon the geometry of the interlayer space and the coordination of the Ca2 site. Whereas the coordination of the Ca1 site is not influenced by the disorder and is trigonal antiprismatic (distorted octahedral), the coordination environment of the Ca2 site includes disordered O atoms and is either trigonal prismatic or trigonal antiprismatic. The observed structural features suggest the possible existence of different varieties of dmisteinbergite that may differ in: (i) degree of disorder of the Al/Si tetrahedral sites, with completely disordered structure having the P63/mcm symmetry; (ii) degree of disorder of the O sites, which may have a direct influence on the coordination features of the Ca2+ cations; (iii) polytypic variations (different stacking sequences and layer shifts). The formation of dmisteinbergite is usually associated with metastable crystallization in both natural and synthetic systems, indicating the kinetic nature of this phase. Information-based complexity calculations indicate that the crystal structures of metastable CaAl2Si2O8 polymorphs dmisteinbergite and svyatoslavite are structurally and topologically simpler than that of their stable counterpart, anorthite, which is in good agreement with Goldsmith’s simplexity principle and similar previous observations.

AB - The crystal structure of dmisteinbergite has been determined using crystals from the type locality in Kopeisk city, Chelyabinsk area, Southern Urals, Russia. The mineral is trigonal, with the following structure: P312, a = 5.1123(2), c = 14.7420(7) Å, V = 333.67(3) Å3, R1 = 0.045, for 762 unique observed reflections. The most intense bands of the Raman spectra at 327s, 439s, 892s, and 912s cm-1 correspond to different types of tetrahedral stretching vibrations: Si-O, Al-O, O-Si-O, and O-Al- O. The weak bands at 487w, 503w, and 801w cm-1 can be attributed to the valence and deformation modes of Si-O and Al-O bond vibrations in tetrahedra. The weak bands in the range of 70-200 cm-1 can be attributed to Ca-O bond vibrations or lattice modes. The crystal structure of dmisteinbergite is based upon double layers of six-membered rings of corner-sharing AlO4 and SiO4 tetrahedra. The obtained model shows an ordering of Al and Si over four distinct crystallographic sites with tetrahedral coordination, which is evident from the average <T-O> bond lengths (T = Al, Si), equal to 1.666, 1.713, 1.611, and 1.748 Å for T1, T2, T3, and T4, respectively. One of the oxygen sites (O4) is split, suggesting the existence of two possible conformations of the [Al2Si2O8]2- layers, with different systems of ditrigonal distortions in the adjacent single layers. The observed disorder has a direct influence upon the geometry of the interlayer space and the coordination of the Ca2 site. Whereas the coordination of the Ca1 site is not influenced by the disorder and is trigonal antiprismatic (distorted octahedral), the coordination environment of the Ca2 site includes disordered O atoms and is either trigonal prismatic or trigonal antiprismatic. The observed structural features suggest the possible existence of different varieties of dmisteinbergite that may differ in: (i) degree of disorder of the Al/Si tetrahedral sites, with completely disordered structure having the P63/mcm symmetry; (ii) degree of disorder of the O sites, which may have a direct influence on the coordination features of the Ca2+ cations; (iii) polytypic variations (different stacking sequences and layer shifts). The formation of dmisteinbergite is usually associated with metastable crystallization in both natural and synthetic systems, indicating the kinetic nature of this phase. Information-based complexity calculations indicate that the crystal structures of metastable CaAl2Si2O8 polymorphs dmisteinbergite and svyatoslavite are structurally and topologically simpler than that of their stable counterpart, anorthite, which is in good agreement with Goldsmith’s simplexity principle and similar previous observations.

KW - Burned coal dumps

KW - Crystal structure

KW - Dmisteinbergite

KW - Feldspar

KW - Kopeisk

KW - Metastability

KW - Polymorphism

KW - Raman spectroscopy

KW - Ural region

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U2 - 10.3390/min9100570

DO - 10.3390/min9100570

M3 - Article

AN - SCOPUS:85073417907

VL - 9

JO - Minerals

JF - Minerals

SN - 2075-163X

IS - 10

M1 - 570

ER -