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Zhou, Xiang-Feng

Publications and source records attributed to Zhou, Xiang-Feng.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Magnetic borophenes from an evolutionary search

A computational methodology based on ab initio evolutionary algorithms and spin-polarized density functional theory was developed to predict two-dimensional magnetic materials. Its application to a model system borophene reveals an unexpected rich magnetism and polymorphism. A metastable borophene with nonzero thickness is an antiferromagnetic semiconductor from first-principles calculations, and can be further tuned into a half-metal by finite electron doping. In this borophene, the buckling and coupling among three atomic layers are not only responsible for magnetism, but also result in an out-of-plane negative Poisson's ratio under uniaxial tension, making it the first elemental material possessing auxetic and magnetic properties simultaneously.

2-dimensional systems↗
DOE OSTI2018

Predicting the ground-state structure of sodium boride

Binary borides has been a subject of extensive research. However, the exact compositions and crystal structures of sodium borides remained controversial. Furthermore, using the ab initio variable-composition evolutionary algorithm, a new stable Na 2 B 30 with I2 1 2 1 2 1 symmetry (I2 1 2 1 2 1 –Na 2 B 30 ) is found, which is –7.38 meV / atom lower in energy than the Imma–Na 2 B 30 structure reported by experimentalists. Interestingly, the Imma–Na 2 B 30 structure is predicted to be a topological nodal line semimetal, which may result in superior electronic transport. In contrast, I2 1 2 1 2 1 –Na 2 B 30 is an ultrahard semiconductor with an unprecedented open-framework structure, whose interstitial helical boron sublattice enhances its hardness and energetic stability.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Prediction of a new ground state of superhard compound B6O at ambient conditions

Boron suboxide B 6 O), the hardest known oxide, has an Rm crystal structure (α-B 6 O) that can be described as an oxygen-stuffed structure of α-boron, or, equivalently, as a cubic close packing of B 12 icosahedra with two oxygen atoms occupying all octahedral voids in it. Here we show a new ground state of this compound at ambient conditions, Cmcm-B 6 O) (β-B 6 O)), which in all quantum-mechanical treatments that we tested comes out to be slightly but consistently more stable. Increasing pressure and temperature further stabilizes it with respect to the known α-B 6 O) structure. β-B 6 O) also has a slightly higher hardness and may be synthesized using different experimental protocols. We suggest that β-B 6 O) is present in mixture with α-B 6 O), and its presence accounts for previously unexplained bands in the experimental Raman spectrum.

Science & Technology - Other Topics↗