Effect of the double-counting functional on the electronic and magnetic properties of half-metallic magnets using the GGA+U method

Abstract

Methods based on the combination of the usual density functional theory (DFT) codes with the Hubbard models are widely used to investigate the properties of strongly correlated materials. Using first-principle calculations we study the electronic and magnetic properties of 20 halfmetallic magnets performing self-consistent GGA+U calculations using both the atomic-limit (AL) and around-mean-field (AMF) functionals for the double counting term, used to subtract the correlation part from the DFT total energy, and compare these results to the usual generalized-gradientapproximation (GGA) calculations. Overall the use of AMF produces results similar to the GGA calculations. On the other hand the effect of AL is diversified depending on the studied material. In general the AL functional produces a stronger tendency towards magnetism leading in some cases to unphysical electronic and magnetic properties. Thus the choice of the adequate double-counting functional is crucial for the results obtained using the GGA+U method.

First-principles studies of the Gilbert damping and exchange interactions for half-metallic Heuslers alloys

“…59 and implemented in the FP-LAPW package Elk 60 . It was found that both Co 2 MnSi and Co 2 FeSi are better described with the AMF scheme, as indicated by their small α U parameter of ∼ 0.1 for both materials (α U = 0 denotes complete AMF and α U = 1 FLL), which is in agreement with the recent work by Tsirogiannis and Galanakis 61 . To test whether a more sophisticated way to treat correlation effects improves the description of these materials, electronic structure calculations for Co 2 MnSi and Co 2 FeSi using the DMFT scheme were performed.…”

Ab-initio investigation of electronic and magnetic properties of the 18-valence-electron fully-compensated ferrimagnetic (CrV)XZ Heusler compounds: A prototype for spin-filter materials

“…Due to the existence of the energy gaps in the electronic band structure one could envisage using also approximations beyond the standard functionals like (a) the orbital dependent functionals [34], (ii) the Hubbard LDA + U schemes [35,36], or (iii) hybrid functionals like the Heyd-Scuseria-Ernzerhof functional [37,38]. Such schemes are known to alter in several cases the results obtained with the standard LDA or GGA schemes, and sometimes they also produce contradictory results.…”

A first-principles DFT+ GW study of spin-filter and spin-gapless semiconducting Heusler compounds

“…In particular, the GW approach corrects the band gaps from their (usually underestimated) DFT values towards experiment. Furthermore, it is known to produce more accurate results for halfmetallic Heusler compounds than other simplified approaches such as GGA+U [60,61]. For the half-metallic Heusler compounds Co 2 MnSi and Co 2 FeSi, it has also been shown to be able to accurately reproduce the experimental photoemission and x-ray absorption spectra [62].…”