Tuning the Magnetism in Boron-Doped Strontium Titanate

The magnetic and electronic properties of boron-doped SrTiO₃ have been studied by first-principles calculations. We found that the magnetic ground states of B-doped SrTiO₃ strongly depended on the dopant-dopant separation distance. As the dopant–dopant distance varied, the magnetic ground states of B-doped SrTiO₃ can have nonmagnetic, ferromagnetic or antiferromagnetic alignment. The structure with the smallest dopant-dopant separation exhibited the lowest total energy among all configurations considered and was characterized by dimer pairs due to strong attraction. Ferromagnetic coupling was observed to be stronger when the two adjacent B atoms aligned linearly along the B-Ti-B axis, which could be associated with their local bonding structures. Therefore, the symmetry of the local structure made an important contribution to the generation of a magnetic moment. Our study also demonstrated that the O-Ti-O unit was easier than the Ti-B-Ti unit to deform. The electronic properties of boron-doped SrTiO₃ tended to show semiconducting or insulating features when the dopant–dopant distance was less than 5 Å, which changed to metallic properties when the dopant–dopant distance was beyond 5 Å. Our calculated results indicated that it is possible to manipulate the magnetism and band gap via different dopant–dopant separations.

Review of First-Principles Studies of TiO2: Nanocluster, Bulk, and Material Interface

TiO2 has extensive applications in the fields of renewable energy and environmental protections such as being used as photocatalysts or electron transport layers in solar cells. To achieve highly efficient photocatalytic and photovoltaic applications, ongoing efforts are being devoted to developing novel TiO2-based material structures or compositions, in which a first-principles computational approach is playing an increasing role. In this review article, we discuss recent computational and theoretical studies of structural, energetic, electronic, and optical properties of TiO2-based nanocluster, bulk, and material interface for photocatalytic and photovoltaic applications. We conclude the review with a discussion of future research directions in the field.

Band Gap Engineering of In2TiO5 for H2 Production under Near-infrared Light

In2TiO5, containing both early transition metal (d(0)) and p-block metal (d(10)), is a very promising candidate for possible application in H2 production because of its suitable edges of conduction and valence bands and the crystal structure, which is considered to favor mobility of charge carriers. Herein we report, for the first time, the synthesis of novel oxygen vacancies (OV), N-doped In2TiO5 (OV,N-In2TiO5) with controllable band gap. The resultant OV,N-In2TiO5 sample was prepared by a multistep sol-gel calcination process and studied as a near-infrared (NIR) light-driven photocatalyst for H2 production. OV and N-doping can effectively extend the photoresponse of In2TiO5 to the NIR region due to an interband springboard and the reduced band gap, thus leading to efficient NIR light photocatalytic H2 production activity with Pt as a cocatalyst.

Origin of enhanced visible light driven water splitting by (Rh, Sb)-SrTiO3

The origin of enhancement of photoconversion efficiency of Rh-doped SrTiO₃ with the codoping of Sb has been investigated using the hybrid density functional theory. Partially occupied t_2g subset of Rh 4d orbitals is completely filled in the presence of Sb, resulting in the formation of a continuous band structure. This improves the mobility of charge carriers and reduces the electron–hole recombination rate.

N,F-monodoping and N/F-codoping effects on the electronic structures and optical performances of Zn2GeO4

With N/F codoping, the optical absorption property of Zn₂GeO₄was improved under visible-light irradiation, which may promote the photocatalytic activity.

A hybrid DFT based investigation of the photocatalytic activity of cation–anion codoped SrTiO3 for water splitting under visible light

The effect of cation (Mo or W) and anion (N) codoping in different proportion has been explored to improve the photocatalytic activity of SrTiO₃ under visible light. Codoping in 1 : 2 ratio has been found to be more effective due to reduction in band gap without introducing local trapping center and also for maintaining appropriate band alignment.

Strain-engineered modulation on the electronic properties of phosphorous-doped ZnO

The modulation of strain on the electronic properties of ZnO:P is investigated by density functional theory calculations. The variation of formation energy (E(f)) and band structure with strains ranging from -0.1 to 0.1 are considered. Although both the conduction band minimum (CBM) and the valence band maximum of ZnO are antibonding states, the CBM is more sensitive to strain, reducing the band gap with an increase in strain. P-substituted O (PO) defects show poor p-type conductivity due to a smaller E(f) and lower lying acceptor levels as a consequence of lattice expansion. The E(f) of P-substituted Zn (PZn) defects decreases under tension, owing to the release of strong repulsive stress induced by excess electrons from PZn. The donor energy band of PZn broadens under tensile strain, which benefits n-type conductivity. For Zn vacancies (VZn) and PZn-2VZn complexes, the distances between the O atoms around VZn are so large that repulsive and attractive interactions become weak, which results in an easy release of the strain. We herein present for the first time that the E(f) values of VZn and PZn-2VZn complexes decrease under both tension and compression, or in the high-pressure rock-salt phase. Under a strain of 0.1 the PZn-2VZn complex shows the smallest E(f). Under -0.07 strain the wurtzite/rock-salt phase transition occurs and the direct band gap becomes an indirect one. The variation of band structures in the rock-salt phase is similar to that in the wurtzite phase. Consequently, the p-type conductivity of ZnO:P can be improved with an increase in solubility of PZn-2VZn or VZn defects.