Crystal-chemical, vibrational and electronic properties of 1M-phlogopite K(Mg,Fe)3Si3AlO10(OH)2 from Density Functional Theory simulations

Abstract

Trioctahedral micas are peculiar minerals that may present interesting electronic properties that can be modulated by specific cationic substitutions. In the present work, a detailed characterization of the structural, vibrational, and electronic properties of 1M-phlogopite as a function of the FeII/MgII substitutions, with Mg/Fe ratio ≥ 2, is reported. The results were obtained from density functional theory simulations at the B3LYP-D* level of theory, which included the effect of long-range interactions, and also using all-electron Gaussian-type orbitals to describe the atoms in the mineral. The crystal structures of the different phlogopite models were in good agreement with previous X-ray and neutron diffraction data reported in the literature. In addition, the simulated Raman spectra well described the experimental ones obtained from confocal Raman micro-spectrometry, providing additional information on the atomic motions. The electronic band structure and the atom- and orbital-projected density of states were also discussed, describing the nature of the band gap and electronic transitions, and how they vary with the iron content.