Origin of the Room-Temperature Ferromagnetism in Sr₃YCo₄O_10+δ (0.5 < δ < 1.0): Formation of Ferromagnetic Spin Bags in the Oxygen-Rich Perovskite Layers

Origin of the Room-Temperature Ferromagnetism in Sr₃YCo₄O_10+δ (0.5 < δ < 1.0): Formation of Ferromagnetic Spin Bags in the Oxygen-Rich Perovskite Layer

Predicting New TiO₂ Phases with Low Band Gaps by a Multiobjective Global Optimization Approach

TiO₂ has been extensively studied due to the possible application in solar cells and photoelectrochemical (PEC) water-splitting. However, the energy conversion efficiency is rather low because of the large band gaps (larger than 3.0 eV) of rutile and anatase TiO₂. Here we introduce the multiobjective differential evolution (MODE) method as a novel global optimization algorithm to predict new polymorphs of bulk TiO₂ with better optical properties than rutile and anatase TiO₂. The band gaps of the new PI (<i>Pnma</i>) and CI (C2) phases are found to be 1.95 and 2.64 eV. The calculation of formation energy, phonon dispersions, and thermal stability shows that the two novel phases are dynamically and thermally stable. These new TiO₂ polymorphs with better electronic and optical properties may pave a new way for high-efficiency solar energy conversion

Multinational companies in the cleaning industry Local government privatisation, trade union responses and the European dimension

SIGLEAvailable from British Library Document Supply Centre- DSC:DX185562 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Two-Dimensional Hexagonal Transition-Metal Oxide for Spintronics

Two-dimensional materials have been the hot subject of studies due to their great potential in applications. However, their applications in spintronics have been blocked by the difficulty in producing ordered spin structures in 2D structures. Here we demonstrated that the ultrathin films of recently experimentally realized wurtzite MnO can automatically transform into a stable graphitic structure with ordered spin arrangement via density functional calculation, and the stability of graphitic structure can be enhanced by external strain. Moreover, the antiferromagnetic ordering of graphitic MnO single layer can be switched into half-metallic ferromagnetism by small hole-doping, and the estimated Curie temperature is higher than 300 K. Thus, our results highlight a promising way toward 2D magnetic materials

Si₃AlP: A New Promising Material for Solar Cell Absorber

First-principles calculations were performed to study the structural and optoelectronic properties of the newly synthesized nonisovalent and lattice-matched (Si₂)_0.6(AlP)_0.4 alloy (Watkins, T.; et al. <i>J. Am. Chem. Soc.</i> <b>2011</b>, <i>133</i>, 16212). We found that the most stable structure of Si₃AlP is a superlattice along the ⟨111⟩ direction with separated AlP and Si layers, which has a similar optical absorption spectrum to silicon. The ordered <i>C</i>1<i>c</i>1-Si₃AlP is found to be the most stable one among all structures with a basic unit of one P atom surrounded by three Si atoms and one Al atom, in agreement with experimental suggestions. We predict that <i>C</i>1<i>c</i>1-Si₃AlP has good optical properties, i.e., it has a larger fundamental band gap and a smaller direct band gap than Si; thus, it has much higher absorption in the visible light region. The calculated properties of Si₃AlP suggest that it is a promising candidate for improving the performance of the existing Si-based solar cells. The understanding on the stability and band structure engineering obtained in this study is general and can be applied for future study of other nonisovalent and lattice-matched semiconductor alloys