DFT-GIPAW 27Al NMR Simulations for Intermetallics: Accuracy Issues and Magnetic Screening Mechanisms

Abstract

This study reports first-principles simulations of 27Al solid-state nuclear magnetic resonance (ssNMR) shifts (δisoexp) carried out for a set of seven Al-containing intermetallic compounds. With the aim of assessing accuracy issues in such calculations using the gauge-including projector augmented waves method, the referred set was sought to cover the wide range of experimental 27Al δisoexp shifts reported in the literature for this type of compound in a representative way (from about −200 to 1600 ppm). From a technical/computational perspective, the findings allowed the detection of critical sources of inaccuracy and they were addressed to different approximations inherent in the computational methods. Among those, it is possible to highlight the formulation of the exchange-correlation energy functional in density functional theory, which at least for the 27Al nuclide has proved to be more critical than the frozen-core approximation, especially in the case of weakly magnetic aluminides. From a practical ...