The work function is one of the most fundamental surface properties of a material, and understanding and controlling its value is of central importance for manipulating electron flow in applications ranging from high power vacuum electronics to oxide electronics and solar cells. Recent computational studies using Density Functional Theory (DFT) have demonstrated that DFT-calculated work function values for metals tend to agree well (within about 0.3 eV on average) with experimental values. However, a detailed validation of DFT-calculated work functions for oxide materials has not been conducted and is challenging due to the complex dipole structures that can occur on oxide surfaces. In this work, we have focused our investigation on the widely studied perovskite SrTiO3 as a case study example. We find that DFT can accurately predict the work function values of clean and reconstructed SrTiO3 surfaces vs experiment at about the same level of accuracy as metals when direct comparisons can be made. Furthermore, to aid in understanding the factors governing the work function of oxides, we have performed systematic studies on the influence of common surface features, including surface point defects, doping, adsorbates, reconstructions, and surface steps, on the work function. The relationships between the surface structure and work function for SrTiO3 identified here may be qualitatively applicable to other complex oxide materials.

High throughput DFT simulations yield 7 low work function perovskites as promising cathode materials.

In this study, the effect on the structure stability, elastic properties and electronic structure of P-doped Mg 2 Si were studied by the first-principles pseudopotential plane wave method based on density functional theory. The lattice constants, formation enthalpy, cohesive energy, elastic constants, and elastic moduli of Mg 2 Si, Mg 7 Si 4 P, Mg 8 Si 3 P and Mg 8 Si 4 P were calculated, and the electronic structure analysis was also performed. The occupation tendency, structural stability, bonding characteristics, orbital hybridization and the change of conductivity of doping P atoms in the matrix were further investigated. Among them, the research results of formation enthalpy, cohesive energy and elastic constant show that Mg 2 Si, Mg 8 Si 3 P and Mg 8 Si 4 P can all exist stably in the system, and the crystal structure of Mg 7 Si 4 P can not exist stably. P atoms doping into the Mg 2 Si lattice tend to occupy Si atoms position preferentially. The results of elastic modulus study show that Mg 2 Si and Mg 8 Si 4 P are brittle phase and Mg 8 Si 3 P is ductile phase. The plasticity and toughness of Mg 2 Si alloy system are improved by doping P atoms. The electronic structure analysis shows that the method of doping P atoms changes the orbital hybridization and bonding characteristics of the system. The Mg-P and Si-P covalent bond formed by Mg 8 Si 3 P and Mg 8 Si 4 P increase the structure stability. The energy band structure analysis also show reduction of the band gap from 0.224 to 0.184 eV for Mg 2 Si with P dopants at the substitutional Si-sites and the band gap closure in the system with interstitial P-impurities. It enhances the metallic property of the material, and Mg 8 Si 4 P phase also transform from its semiconducting to metallic state. Consequently, this method both increases the carrier concentration and reduces the energy of free electron transition. The conductivity of the Mg 2 Si alloy system will be improve.

Herein, the effects of Cu doping with different concentrations on the stability, elastic properties, and electronic structure of Mg2Si are investigated by first‐principles calculations based on density functional theory. The research results show that Mg2Si and Mg8−xSi4−yCux+y (x, y) = {(0.125, 0), (0, 0.125), (0.25, 0), (0, 0.25), (0.5, 0), (0, 0.5), (1, 0), (0, 1)} are stable in the system. The Cu atoms tend to preoccupy Mg sites in Mg2Si lattices, and the alloying ability is stronger than that of Mg8Si4−yCuy (y = 0.125, 0.25, 0.5, 1). Although all dopants are brittle phases, the doping behavior of Cu atoms improves the elastic and plastic properties of the Mg2Si alloy system. The bonding modes of the crystal are also changed. The SiCu covalent bond formed by Mg8−xSi4Cux (x = 0.125, 0.25, 0.5, 1) further increases the structure stability. Meanwhile, Mg7Si4Cu and Mg8Si3Cu are changed from semiconducting to metallic state by energy band structure analysis. It not only increases the carrier concentration, but also reduces the free electron transition energy, which improves the conductivity of the intrinsic Mg2Si. These investigations will provide some theoretical basis for the application of Mg2Si intermetallic compounds in structural materials and thermoelectric materials.

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