Identifying the ground state structures of point defects in solids

Abstract

Point defects are a universal feature of crystals. Their identification is addressed by combining experimental measurements with theoretical models. The standard modelling approach is, however, prone to missing the ground state atomic configurations associated with energy-lowering reconstructions from the idealised crystallographic environment. Missed ground states compromise the accuracy of calculated properties. To address this issue, we report an approach to navigate the defect configurational landscape using targeted bond distortions and rattling. Application of our workflow to eight materials (CdTe, GaAs, Sb2S3, Sb2Se3, CeO2, In2O3, ZnO, anatase-TiO2) reveals symmetry breaking in each host crystal that is not found via conventional local minimisation techniques. The point defect distortions are classified by the associated physico-chemical factors. We demonstrate the impact of these defect distortions on derived properties, including formation energies, concentrations and charge transition levels. Our work presents a step forward for quantitative modelling of imperfect solids.

Cation disorder dominates the defect chemistry of high-voltage LiMn1.5Ni0.5O4 (LMNO) spinel cathodes

“…51,52 A lean version of the ShakeNBreak 53 approach was used to aid the location of the ground-state defect structures. 54,55 With access to the ground state and many metastable defect structures, defect configuration landscape can be explored. This is important for magnetic materials, whereby the magnetic moment of defect structure forms an additional dimension of potential energy surface.…”

“…SnO 2 and BaSnO 3 ). 54,110,116 We identied two distinct O i peroxide congurations with different TM environments: surrounded by 3Mn 4+ and a Ni 2+ (ground state) and surrounded by 2Mn 4+ and 2Ni 2+ (0.8 eV higher in energy).…”

“…In each case, different degrees of structural perturbation (rattling) and magnetisation initialisations were tested, to aid the location of the true ground state defect. [53][54][55] One spin ip usually gives less than 0.1 eV difference in energy. However, multiple spin ips can lead to a large energy change (e.g.…”

Cu₂SiSe₃ as a promising solar absorber: harnessing cation dissimilarity to avoid killer antisites

“…To aid the search for the ground state structures, the ShakeNBreak package was used to find any energy-lowering reconstructions at defect sites. 47,48 In order to account for spurious interactions between charged defects and their periodic image in the DFT supercell approach, the eFNV charge correction scheme was employed. 58,59 Defect concentrations were determined through the calculation of the self-consistent Fermi level as implemented in py-sc-fermi.…”

Cu2SiSe3 as a promising solar absorber: harnessing cation dissimilarity to avoid killer antisites

“…32 The remaining defect states with a formation energy below 1.5 eV, which will form in signicant concentrations depending on the growth conditions, are the Cu Si antisite and V Si . These defects behave similarly due to the ShakeNBreak 47,48 method nding that the lowest energy conguration of a V Si defect is actually a Cu Si + V Cu complex. This rearrangement occurs due to the high Si IV oxidation state, resulting in it being unfavorable to leave the site unoccupied and the low energy of formation of a V Cu leading to a mobile cation.…”