DFT simulation on the temperature-dependent electronic transition of V (Nb or Ta) substituted NiMn2O4

Abstract

Previously, we reported that the [Formula: see text]–[Formula: see text] (Mn-[Formula: see text]–O-[Formula: see text]) orbital hybridization induces Mn valence change (Mn[Formula: see text]Mn[Formula: see text]) in the octahedron. The electron transfer mechanism can be controlled by modifying the Mn-[Formula: see text] orbital in the octahedron. Here, we used the density functional theory (DFT) with generalized gradient approximation (GGA) and two-dimensional correlation analysis (2D-CA) techniques to calculate the electron transfer mechanism of the V (Nb or Ta) substituted NiMn2O4 (NMO) in the temperature range of 50–1500 K. The results show that the heat accumulation accelerates the O-[Formula: see text] orbital splitting, inducing charge disproportionation. The V-[Formula: see text] substituted Mn increases the intensity and of the partial density of state (PDOS) at conduction band (1–3 eV), this enhances the V-[Formula: see text]–O-[Formula: see text] [Formula: see text]–[Formula: see text] [Formula: see text] orbital. The Nb-[Formula: see text]/Ta-[Formula: see text] substituted Mn reduces the intensity of the PDOS at conduction band (1–5 eV), this weakens the Nb-[Formula: see text]/Ta-[Formula: see text]–O-[Formula: see text] [Formula: see text]–[Formula: see text] [Formula: see text] orbital. This study effectively analyzes the microscopic changes of the electron transfer caused by the heat accumulation, provides a theoretical basis for the design of NMO-based negative temperature coefficient (NTC) thermistors.