Electronic properties of fluorides by efficient approximated quasiparticle DFT-1/2 and PSIC methods: BaF₂, CaF₂and CdF₂as test cases

Abstract

Dialkali halides are materials of great interest from both fundamental and technological viewpoints, due to their wide transparency range. The accurate determination of their electronic, excitation and optical properties in bulk and low dimensional systems is therefore of crucial importance. Moreover, it is a challenge from the theoretical point of view to deal with quasiparticle band structure calculations for such large energy gap materials, requiring very expensive methods for achieving a desirable accuracy. Here we report electronic quasiparticle band structures for three representative bulk fluorides, BaF, CaF and CdF, calculated using two low computational cost methods, the DFT-1/2 and the PSIC schemes, which have been relatively little explored by the theoretical community so far. Our results, compared with both available experimental data and previous heavyweight DFT-GW self-energy calculations, demonstrate a satisfactory accuracy for the examined compounds, at a level comparable with the perturbative GW approach. Remarkably, both our proposed methods scale quite similarly to standard local density functional approaches, thus resulting in a large saving of computational effort with respect to the computationally heavyweight GW. Our results open up the perspective of the computational exploration of much bigger fluoride systems. As a significant proof of concept of this capability, we also calculated the quasiparticle properties of the (1 1 1) surfaces of all the three systems under study. Very good agreement with experiment was found.

Limitations of the DFT–1/2 method for covalent semiconductors and transition-metal oxides

“…37 Another comparative study of DFT-1/2 to the pseudo-self-interaction-corrected approach to DFT was performed on fluorides. 38 Furthermore, a few magnetic systems have been studied, namely GaMnAs 39 and InN doped with Cr. 30 We also mention that the method has recently been applied successfully for the calculation of the ionization potential of atoms and molecules.…”

Electronic and Optical Properties of Small Metal Fluoride Clusters

“…The comparison between the ground- and excited-state properties of the clusters in Tables and and those of the corresponding bulk systems in Tables and may help to understand the effect of nanostructuring on electronic and optical properties. In Table , the ground- and excited-state properties of bulk cubic CaF 2 and BaF 2 are reported. , The computational schemes used to tackle bulk properties are DFT methods based on ionic pseudopotentials and a plane wave expansion of the electronic wave functions. , The reported observables are the distance between metal and fluorine atoms, R ′ M–F , and the vertical ionization energy and electron affinity, IE V and EA V , respectively. IE V and EA V are calculated as differences of energy levels for the (111) surface within a DFT-GGA scheme as difference of energy levels defining the vacuum level by the average electrostatic potential .…”

Fundamentals of tin iodide perovskites: a promising route to highly efficient, lead-free solar cells

“…An interesting alternative is represented by the DFT-1/2 method, 69 which was recently used for stannates, [70][71][72] and can be considered a simplied version of the VPSIC (a comparison of these two approaches can be found in ref. 73).…”