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Title: The Crystal Structures, Solid Solutions and Infrared Spectra of Copiapite-Group Minerals

Abstract

Copiapite is a mineral of iron- and sulphate-rich acidic environments and has a general formula AFe43+(SO4)6(OH)2(H2O)20, where A = Fe2+, 2/3Fe3+, 2/3Al3+, Mg, Zn. The structure is built by infinite tetrahedral-octahedral chains and isolated octahedrally coordinated A sites. Our synthetic and natural copiapite samples can be divided into two large groups based on the orientation of the structural fragments. One group comprises copiapite phases where A = Al3+, Fe2+ or Fe3+ and we designate it as the structural type AL. The other group consists of copiapite with A = Mg2+, Zn2+ or Ni2+ and this is the structural type MG. The solid-solution series between Fe3+ and Al3+ copiapite is continuous. The series between Mg2+-Al3+, Mg2+-Fe3+ and Mg2+-Al3+-Fe3+ copiapite are not continuous; the samples with intermediate compositions contain two copiapite phases, one of the type AL and one of the type MG. The series between Mg2+ and Zn2+ copiapite is continuous only at 25 C. At 75 C, the Zn-rich portion of this system crystallizes a copiapite-like phase whose structure may be a superstructure of copiapite. The series between Al-Fe2+ and Mg-Fe2+ copiapite are not continuous and show complex behaviour of the intermediate compositions.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
960035
Report Number(s):
BNL-83021-2009-JA
Journal ID: ISSN 0026-461X; MNLMBB; TRN: US201016%%1179
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Mineralogical Magazine; Journal Volume: 71; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CHAINS; CRYSTAL STRUCTURE; INFRARED SPECTRA; IRON; ORIENTATION; SOLID SOLUTIONS; national synchrotron light source

Citation Formats

Majzlan,J., and Michallik, R.. The Crystal Structures, Solid Solutions and Infrared Spectra of Copiapite-Group Minerals. United States: N. p., 2007. Web. doi:10.1180/minmag.2007.071.5.553.
Majzlan,J., & Michallik, R.. The Crystal Structures, Solid Solutions and Infrared Spectra of Copiapite-Group Minerals. United States. doi:10.1180/minmag.2007.071.5.553.
Majzlan,J., and Michallik, R.. Mon . "The Crystal Structures, Solid Solutions and Infrared Spectra of Copiapite-Group Minerals". United States. doi:10.1180/minmag.2007.071.5.553.
@article{osti_960035,
title = {The Crystal Structures, Solid Solutions and Infrared Spectra of Copiapite-Group Minerals},
author = {Majzlan,J. and Michallik, R.},
abstractNote = {Copiapite is a mineral of iron- and sulphate-rich acidic environments and has a general formula AFe43+(SO4)6(OH)2(H2O)20, where A = Fe2+, 2/3Fe3+, 2/3Al3+, Mg, Zn. The structure is built by infinite tetrahedral-octahedral chains and isolated octahedrally coordinated A sites. Our synthetic and natural copiapite samples can be divided into two large groups based on the orientation of the structural fragments. One group comprises copiapite phases where A = Al3+, Fe2+ or Fe3+ and we designate it as the structural type AL. The other group consists of copiapite with A = Mg2+, Zn2+ or Ni2+ and this is the structural type MG. The solid-solution series between Fe3+ and Al3+ copiapite is continuous. The series between Mg2+-Al3+, Mg2+-Fe3+ and Mg2+-Al3+-Fe3+ copiapite are not continuous; the samples with intermediate compositions contain two copiapite phases, one of the type AL and one of the type MG. The series between Mg2+ and Zn2+ copiapite is continuous only at 25 C. At 75 C, the Zn-rich portion of this system crystallizes a copiapite-like phase whose structure may be a superstructure of copiapite. The series between Al-Fe2+ and Mg-Fe2+ copiapite are not continuous and show complex behaviour of the intermediate compositions.},
doi = {10.1180/minmag.2007.071.5.553},
journal = {Mineralogical Magazine},
number = 5,
volume = 71,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Solid solutions of the ammonium Cr/Zn Tutton salt with two different compositions, (NH{sub 4}){sub 2}[Cr{sub 0.10}Zn{sub 0.90}(H{sub 2}O){sub 6}]-(SO{sub 4}){sub 2}, 1, and (NH{sub 4}){sub 2}[Cr{sub 0.22}Zn{sub 0.78}(H{sub 2}O){sub 6}](SO{sub 4}){sub 2}, 2, have been studied by single-crystal X-ray diffraction at room temperature and by single crystal time-of-flight neutron diffraction at 11-16 K for 1 and at 11-17 K for 2. Composition was also characterized by atomic absorption, AA, analysis. The solid solutions crystallize in the monoclinic space group P2{sub 1}/c, Z = 2. The structure of 1 was refined to residuals of R = 0.0226 and 0.0670 and qualitymore » of fit = 1.099 and 1.165 for X-ray and neutron data, respectively; the corresponding residuals for the X-ray and neutron structures of 2 are R = 0.0215 and 0.0682, and quality-of-fit = 1.057 and 0.994. The anisotropic displacement parameters of the oxygen and hydrogen atoms from the neutron diffraction studies are examined for their implications as to the presence or absence of disorder in the ligands about the composite Cr/Zn metal center. The results for composition 2, x(Cr) = 0.22, clearly indicate the presence of disorder for the aqua ligand affected by Jahn-Teller distortion in the pure chromium complex. For composition 1, x(Cr) = 0.10, the observation of disorder is not clear. The structures of 1 and 2 are isotypic at a given temperature, but the room-temperature and low-temperature structures differ subtly in the hydrogen bonding pattern.« less
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  • Fourier-transform infrared spectroscopy is a valuable method for the study of protein conformation in solution primarily because of the sensitivity to conformation of the amide I band (1700-1620 cm{sup {minus}1}) which arises from the backbone C{double bond}O stretching vibration. Combined with resolution-enhancement techniques such as derivative spectroscopy and self-deconvolution, plus the application of iterative curve-fitting techniques, this method provides a wealth of information concerning protein secondary structure. Further extraction of conformational information from the amide I band is dependent upon discerning the correlations between specific conformation types and component bands in the amide I region. In this paper the authorsmore » report spectra-structure correlations derived from conformational perturbations in bovine trypsin which arise from autolytic processing, zymogen activation, and active-site inhibition. IR spectra were collected for the single-chain ({beta}-trypsin) and once-cleaved, double-chain ({alpha}-trypsin) forms as well as at various times during the course of autolysis and also for zymogen, trypsinogen, and {beta}-trypsin inhibited with diisopropyl fluorophosphate. Spectral differences among the various molecular forms were interpreted in light of previous biochemical studies of autolysis and the known three-dimensional structures of the zymogen, the active enzyme, and the DIP-inhibited form. The spectroscopic results from these proteins in D{sub 2}O imply that certain loop structures may absorb in the region of 1655 cm{sup {minus}1}. They estimate that this approach to data analysis and interpretation is sensitive to changes of 0.01 unit or less in the relative integrated intensities of component bands in spectra whose peaks are well resolved.« less
  • No abstract prepared.
  • Condensation of ethylene molecules and alkali metal atoms at high dilution in argon produced very different results, depending on the nature of the alkali metal. While heavy alkali metal atoms (Na and Cs) yielded only a very weak complex with ethylene virtually unperturbed, lithium gave evidence for Li/sub 2/C/sub 2/H/sub 4/ and Li(C/sub 2/H/sub 4/)/sub n/ (n = 1,2,3) displaying large perturbations in the ethylene ligand. Isotopic substitutions (/sup 6/Li, /sup 7/Li, C/sub 2/H/sub 4/, /sup 13/C/sub 2/H/sub 4/, C/sub 2/D/sub 4/, and CH/sub 2/CD/sub 2/) showed that the metal center forms a ..pi.. complex with equivalent CH/sub 2/ groupsmore » in each structure and that the ligands are equivalent in lithium di- and triethylene. Simplified normal-coordinate analyses show that the C=C bond force constant is lowered by approximately 30%, 21%, and 16% in Li(C/sub 2/H/sub 4/)/sub n/ with n = 1, 2, and 3, respectively, whereas the CH/sub 2/ bending force constant is very little altered relative to ethylene. An analysis of the infrared intensities shows that the strong IR activity of the three Li(C/sub 2/H/sub 4/)/sub n/ species is likely to be due to a large variation in charge flow between metal and C=C groups upon variation of the C=C bond distance and, to a lesser extent, upon CH/sub 2/ bond angle variation. The spectrum of the dilithium species indicates nonequivalent metal atoms and is best explained by fixation of the second metal on the first metal center, which is thought to account for the strengthening of the C-Li bonds and the further puckering of the C/sub 2/H/sub 4/ group.« less