High-throughput computational materials screening of transition metal peroxides.

Semiconductor materials of abnormal stoichiometric ratio often exhibit unique properties, yet it is still a challenge to determine the structures of such materials in an efficient way. Herein, we propose a method for structurally biased screening according to the coordination numbers and the numbers of Wyckoff positions, balancing the atom local environment and the global symmetry of structures. Based on first-principles calculations, we have predicted two metastable peroxides P21/c-ScO2 and Pmmn-TiO3 with more than six coordination points. For these two structures, the most stable intrinsic defect is the oxygen vacancy (VO) at the peroxide anion (O2-2), which induces the absence of antibonding orbital formed by O2-2 near the valence band maximum. With the introduction of VO, the decrease of coordination numbers leads to charge recombination, and results in the appearance of an ordered phase TiO2.5 with stronger Ti-O orbital hybridization. The proposed method presents a promising and feasible approach for the screening of novel compounds.

Five-fold symmetry in Au-Si metallic glass.

The first metallic glass of Au-Si alloy for over half a century has been discovered, but its atomic structure is still puzzling. Herein, Au8Si dodecahedrons with local five-fold symmetry are revealed as building blocks in Au-Si metallic glass, and the interconnection modes of Au8Si dodecahedrons determine the medium-range order. With dimensionality reduction, the surface ordering is attributed to the motif transformation of Au8Si dodecahedrons into planar Au5Si pyramids with five-fold symmetry, and thus the self-assembly of Au5Si pyramids leads to the formation of the ordered Au2Si monolayer with the lowest energy. Furthermore, structural similarity analysis is performed to unveil the physical origin of the structural characteristics in different dimensions. The amorphism of Au-Si is due to the smooth energy landscape around the global minimum, while the ordered surface structure occurs due to the steep energy landscape.

Developing Proton-Conductive Metal Coordination Polymer as Highly Efficient Electrocatalyst toward Oxygen Reduction.

Developing earth-abundant transition metal (TM)-based electrocatalysts toward oxygen reduction reaction (ORR) is significant in overcoming the high cost of fuel cells. Herein, using an as-synthesized proton-conductive coordination polymer (termed TM-DHBQ) as a template, we investigate the ORR performance of a series of such TM-DHBQs via screening 3d, 4d, and 5d TMs. We find that most 3d TM-DHBQs exhibit distinguished durability under ORR turnover conditions. The formation energies of these TM-DHBQs and adsorption free energies of ORR intermediates show a good correlation with the number of outer electrons of TM ions in TM-DHBQs, enabling the formation energy as a robust ORR activity descriptor. The Sabatier-type volcano plot and microkinetic modeling coidentify Fe- and Co-DHBQs as two promising alternatives to Pt-based ORR electrocatalysts. For those TM-DHBQs showing strong bonding to oxygen species, the ORR intermediate is found to combine with the TM ion serving as the active center.

All-boron planar ferromagnetic structures: from clusters to monolayers.

Ferromagnetism in all-boron planar clusters is revealed based on high-throughput first-principles calculations. Magnetic boron clusters induced from p electrons have been confirmed with large spins, e.g., S = 3 in a B34 cluster, which can be assembled to construct all-boron ferromagnetic monolayers. Notably, the ferromagnetic semiconductors of boron monolayers can be designed with the hybridization of a nonmagnetic B36 cluster in experimental synthesis. The ferromagnetism-paramagnetism transition and semiconductor-metal transition in these boron nanostructures will occur around 500 K according to ab initio molecular dynamics simulation, indicating the potential applications in nano-devices at room temperature. The coexisting ferromagnetic and semiconducting properties in boron monolayers are attributed to the unique multicenter bonds together with the modulation of structural symmetry, which might be worth experimental attempts in the future.

Theoretical study of tunable magnetism of two-dimensional MnSe2through strain, charge, and defect.

Two-dimensional transition metal dichalcogenide MnSe2(2D-MnSe2) with Curie temperature approximate to 300 K has a significant spintronic application on thin-film devices. We demonstrate theoretically a tunable magnetic transition of 2D-MnSe2between anti-ferromagnetic (AFM) metal and ferromagnetic (FM) half metal as strain increasing. Mechanism of that transition involves a competition betweend-p-dthrough-bond andd-ddirect interaction in 2D-MnSe2. Hole doping is an alternative way to enhance the stability of FM coupling. Adsorption (including Li, Na, Cl and F) and vacancy (Mn and Se) studies confirm that the controllable magnetism of 2D-MnSe2is related to both interaction competition and charge doping. Tensile strains can greatly amplify through-bond interaction and exchange parameters, resulting in a sharp increase of Curie temperature.

Atom Classification Model for Total Energy Evaluation of Two-Dimensional Multicomponent Materials.

The tunable properties of materials originate from variety of structures; however, it is still a challenge to give an accurate and fast evaluation of stabilities for screening numerous candidates. Herein, we propose an atom classification model to describe the multicomponent materials based on the structural recognition, in which the atoms are classified to estimate the total energies. Taking two-dimensional planar C1-xBx and C1-2x(BN)x as examples, we have found that the test error of total energies is about 3 meV per atom. Notably, the distributions of classified atoms demonstrate the evolution of configurations as a function of temperature, providing a clearer picture of phase transition. In addition, our method is universal, which can be flexibly extended to the bulk structures with more components.