Na+ as a probe to structural investigation of dehydrated smectites using NMR spectra calculated by DFT

Ab initio calculations based on density-functional theory (DFT) were made to a large ensemble of representative models of dehydrated smectites with Na+ as counterion. The structures were generated by different isomorphic substitutions of Al3+ by Mg2+ in octahedral sheet and Si4+ by Al3+ in tetrahedral sheet followed by full optimization of the geometries. Structures were chosen among the lowest total energies to calculate nuclear magnetic resonance (NMR) parameters of H-1, Al-27, Si-29, Mg-25 and Na-23 by means of gauge including projector augmented wave (GIPAW) method. The calculated NMR parameters and simulated spectra suggest that Na+ can be a good probe to investigate the layer structure. The spectra shape for Na-23 is more sensitive to isomorphic substitutions in the layer than the other nuclei. (C) 2016 Elsevier B.V. All rights reserved.