Superconductivity of boron-doped graphane under high pressure

Structural, electronic and magnetic properties of TlFeSe2under high pressure

The high-pressure (HP) properties of TlFeSe₂are investigated based on the first-principles calculations combined with structure-searching method. The low-pressureC2/mphase will transform into the orthorhombicPnmaphase at 2 GPa, with 8% volume collapse, the insulator-metal transition and the bicollinear antiferromagnetic-to-nonmagnetic spin-crossover. At pressure higher than 8 GPa, the HPC2/mphase will become the ground state. BothPnmaphase and HPC2/mphase are constituted by one-dimensional chains of edge-sharing FeSe₅tetragonal pyramids. Pressuring decrease the Se-Se bond length giving rise to the transition from [Se₂]^3-to [Se₂]^2-. Negative charge transfer causes the Fe²⁺with ∼2 μ_Bmagnetic moment at ambient pressure and the nonmagnetic Fe^1.5+at higher pressure. The Fermi surfaces of HP phases are also discussed.

Boron-dopant enhanced stability of diamane with tunable band gap

The structural, electronic, and superconducting properties of B-doped cubic and hexagonal diamane (single layer diamond) were investigated based on the first-principles methods. B atom tends to stay in the substitutional site, and the most stable configuration is the structure with vertical B-B dimer. The formation energy of B-doped diamane is lower than the counterpart of pristine diamane indicating that B dopant can facilitate the synthesis of diamane. The configurations with vertical B-B dimers are semiconductors with tunable band gaps, which decrease with the B concentration increasing due to the interaction between B-B dimers. For example, the band gap of 3.125 mol% and 6.25 mol% B-doped cubic diamane is 1.82 eV and 1.44 eV, respectively. Moreover, configurations with meta-stable B distributions are metals, which have comparable superconducting transition temperatures with B-doped diamond (~4 K).