Surface effects of on the electronic properties of calcium hexaboride (CaB6): a DFT first-principles study


Calcium hexaboride is part of the metal hexaborides (MB6) materials group which are well characterized compounds with Pm3m symmetry known for their low work functions, high melting points, low thermal expansion coefficients, high hardness, and chemical stability. On this work, the effects of surface anisotropy on the electronic structure of different CaB6 surface configurations is analyzed. Density Functional Theory (DFT) calculations are performed using the plane-wave and pseudopotentials method as implemented by the open-source suite of codes QUANTUM ESPRESSO. The band gap, band structure, and charge density at the surface of CaB6 are calculated to gain insight on the surface effects. The results show a reduced band gap on the surface structures in comparison to the bulk, indicating that the surface atomic tends to have a semi-metallic behavior, while the bulk it is known to be a semiconductor with a band gap of >1.0 eV. These results also have important implications on the design and applications of materials with tunable band gap or applications such as radiation detection for example.

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