Revisiting the crystal structure of dickite: X-ray diffraction, solid-state NMR, and DFT calculations study
authors Rocha, J; Paz, FAA; Sardo, M; Mafra, L
nationality International
journal AMERICAN MINERALOGIST
author keywords Dickite; crystal structure; X-ray diffraction; H-1; Al-27; Si-29 MAS NMR; DFT methods
keywords BOND-VALENCE PARAMETERS; MAS-NMR; KAOLINITE; 1ST-PRINCIPLES; SPECTROSCOPY
abstract Dickite is a member of the family of 1:1 dioctahedral phyllosilicates known as the kaolin minerals, with composition Al2Si2O5(OH)(4). The elucidation of the hydrogen-atom positions in dickite, addressed here, and indeed in other hydrated minerals poses particular challenges. The crystal structure of dickite was determined from single-crystal X-ray diffraction at 100(2) K in the non-centrosymmetric Cc monoclinic space group and found to agree closely with previously reported structures (Bish and Johnston 1993; Dera et al. 2003). Al-27 and Si-29 solid-state NMR spectra of unprecedented resolution bear evidence for two distinct Al and Si sites, being consistent with the previously determined structures. Positions of the four independent hydrogen atoms were optimized and the pertinent H-1 chemical shifts calculated using DFT methods (program CASTEP) and compared with high-resolution MAS NMR experimental data obtained at ultra-high sample spinning rates (up to 67 kHz). This work contributes new evidence on the precise hydrogen-atom positions of dickite, and it illustrates how X-ray diffraction, solid-state NMR, and theoretical calculations may be combined to yield an improved mineral crystal structure.
publisher MINERALOGICAL SOC AMER
issn 0003-004X
year published 2018
volume 103
issue 5
beginning page 812
ending page 818
digital object identifier (doi) 10.2138/am-2018-6294
web of science category Geochemistry & Geophysics; Mineralogy
subject category Geochemistry & Geophysics; Mineralogy
unique article identifier WOS:000431122500013
  ciceco authors
  impact metrics
journal analysis (jcr 2017):
journal impact factor 2.645
5 year journal impact factor 2.450
category normalized journal impact factor percentile 66.227
dimensions (citation analysis):
altmetrics (social interaction):



 


Apoio

1suponsers_list_ciceco.jpg