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

• DFT calculations of 136 smectites were made and the NMR parameters were simulated.
• The isomorphic in the layers affect more the 23Na spectra than the other nuclei.
• The substitutions have influence on chemical shift and quadrupolar constants.
• Na+ ions take place in the charge density transference among the layers.

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 1H, 27Al, 29Si, 25Mg and 23Na 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 23Na is more sensitive to isomorphic substitutions in the layer than the other nuclei.