First-Principles Study on the Structure and Electronic Structure of K and P-Doped Iron-Based Superconductor BaFe2As2

In the process of 25% K and 12.5% P-doped BaFe₂As₂, the decrease of Fe ions height is accompanied by the suppression of antiferromagnetic order. Both K and P-doping cause an increase in the distance between Fe–As layers and a contraction of Fe–As bonds, and the contraction of Fe–As bond seems to be one of the most sensitive factors affecting antiferromagnetic suppression. It is found that the contraction of Fe–As bonds tends to be coordinated with an increase in Fe–Fe average distance to ultimately suppress antiferromagnetism to a smaller value. Similar structural changes result in K/P-doping causing Lifshitz transition (LT) and electronic topological transition (ETT). At the Fermi level, K-doping increases the density of states of Fe 3d and As 4p, while P-doping reduces these values.