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Combining the extended cluster expansion method and the first-principles calculations, we have systematically investigated the structural stabilities of nitrogen doped C 60 fullerene. With the structural recognition, we have calculated all possible isomers of C 60-n N n (n = 1–4) to obtain their ground state structures using the first-principles method. For C 60-n N n (n = 5–9) heterofullerenes, we have estimated the energy by the extended cluster expansion method to screen the candidates efficiently, followed by first-principles confirmation for the low-lying structures. For C 60-n N n with more than 9 nitrogen atoms, we developed a classification method to select the candidates and successfully obtained the low-lying isomers. The most stable structures for C 60-n N n (n = 3–11) we obtained have lower energies compared to the structures in previous studies. Notably, we have found 26 low-lying structures of C 48 N 12 azafullerenes, from their 11.6 billion isomers. We propose an energy prediction method to deal with the numerous nonequivalent structures, highly improving the structural screening efficiency. Firstly, we obtain the ground states of C 60-n N n for n = 2–4 and the interactive energies used for fitting in the ExCE method. Then the ExCE method is used to obtain the low-lying isomers of C 60-n N n for n = 5–9. On the basis of the investigations at 2-body substructures in the calculated azafullerenes, we propose a classification method to filter out the majority of the isomers with low stability, therefore we adopt ExCE method to predict the stability of the rested isomers and obtain the most stable isomers of C 60-n N n for n = 10–12. Apart from C 58 N 2 and C 48 N 12 , all the most stable isomers we obtained have higher stabilities than those of the ones reported in literatures so far. It is found that azafullerenes will not be stable if there is any pentagonal ring with more than one heteroatom, or two nitrogen atoms are in ortho positions of hexagonal rings. For C 48 N 12 heterofullerenes, we have obtained many structures with similar stabilities. Besides the ones predicted by Hultman and Manaa we have found other 24 low-lying isomers whose stabilities are between these two structures. Image 1 [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDs) exhibit many novel properties due to dimension, lattice distortion, electron-electron interaction etc. Here, we determine that 1T-VTe 2 with space group P 3 ‾ m 1 is an antiferromagnetic metal by first-principles calculations, and three metastable structures are predicted, i.e., the P 21 / m and C 2 / m antiferromagnetic semiconductor phases and P 3 m 1 ferrimagnetic half-metal phase. Besides, the C 2 / m phase can be transfered to the P 3 m 1 phase by electron doping, while hole doping can induce a transition from C 2 / m phase to P 3 ‾ m 1 phase. These transitions could be ascribed to a strong coupling of charge, lattice, and spin degrees of freedom in VTe 2. The diverse electronic and magnetic properties of VTe2 provide a good platform for researchers to understand the interactions between spin, charge and lattice. • 1-VTe 2 is clarified to be antiferromagnetic metal ground state. • Three VTe 2 phases with different magnetic states and electronic structures are predicted. • Carrier doping can induce transitions between different phases. • Strong spin-lattice-charge interaction is found in VTe 2. [ABSTRACT FROM AUTHOR]

Hydrogen storage with Ti decorated nano-materials is attributed to the d levels of Ti with unsaturated bonding, whose configuration significantly affects the system's stability and activity. Using first-principles calculations, we have investigated hydrogen adsorption and desorption on the Ti decorated defective graphene under various strains (from 0% to 15%), in which Ti atoms' dispersing are energetically stable. According to the phase diagram, we showed that hydrogen uptake can be modulated as a function of chemical potential and strain, since the strain modifies the configuration of d levels, and consequently affects the binding between H 2 and Ti atom. Remarkably, Ti decorated defective graphene under 15% strain could be considered as an ideal media of hydrogen storage, in which the desorption temperature of H 2 is expected to be ∼300 K at 0.5 atm. The control of strain is found to be dominant to the H 2 uptake, besides the temperature and pressure. [ABSTRACT FROM AUTHOR]

The dispersion of transition metals (TM) has been an ongoing challenge for quasi-molecular H 2 storage. Here we have investigated the adsorption of TM (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) on benzoquinone (BQ), by using the first-principles methods. It is found that Sc or Ti (Sc/Ti) atom is energetically favored to bind with ortho-BQ (OBQ) to form OBQ–Sc/Ti complex when compared to their bulk structures. Notably, the coordination number of Sc/Ti is only two, thereby providing enough empty d orbitals for H 2 storage without geometrical blocking. Four H 2 molecules can be accommodated by each OBQ–Sc complex via Kubas-like interaction, with the adsorption energy of 0.20 eV/H 2 and the H 2 storage capacity of ∼5.0 wt%. For practical application, two types of structures have been proposed for H 2 storage using BQ molecule as building block, which would guarantee the dispersing of Sc atom and avoid clustering of OBQ–Sc complexes. In particular, for Sc-decorated oxygen-terminated zigzag graphene nanoribbons, the capacity of H 2 storage reaches up to 6.0 wt%. [ABSTRACT FROM AUTHOR]

The antiferromagnetic-semiconductor extreme tensile strain (8%) states of La 0.7 Ca 0.3 MnO 3 membranes was achieved by Hong et al. (2020) [23]. To understand such tunable magnetic and electronic properties in these La 2 3 M 1 3 MnO 3 (M=Ca, Sr) systems, we have investigated the magnetic and electronic behaviors of La 2 3 M 1 3 MnO 3 (M=Ca, Sr) under strain and charge doping using first-principles calculations. A ferromagnetic-semiconductor phase is predicted for La 2 3 Sr 1 3 MnO 3 beyond 4% biaxial tensile strain. Meanwhile, its energy gap and magnetic anisotropic energy increase as the strain increases. We also discover that the change of magnetic exchange energy in La 2 3 Ca 1 3 MnO 3 under charge doping is in analogy to the scenario directly changing the Ca concentrations. Based on the magnetic competition analysis, it is expected that the carrier concentration and strains dominate the magnetic ground state while the La/Ca distributions have little impact. The highly tunable magnetic-electronic properties offer opportunities for the future magnetic-electronic materials design and applications. • DFT SCAN calculations give excellent structure and magnetic moments of the studied systems. • A ferromagnetic semiconductor is predicted for La 2/3 Sr 1/3 MnO 3 under biaxial tensile strain. • Carrier concentration combined with strains dominate the magnetic coupling. • Magnetic anisotropic energy is enhanced by 30 μeV by strains for La 2/3 Sr 1/3 MnO 3. [ABSTRACT FROM AUTHOR]