Screened-exchange determination of the optical properties of large gap insulators: CaF2

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Abstract
Optical measurements have provided an extremely difficult challenge to existing electronic band structure calculations. Although CaF 2 , an important large gap insulator, has been intensively investigated, no parameter-free first-principles calculations have been done due to the well-known failure of the local density approximation (LDA) in treating excited states. Here, we present results of fully first-principles calculations of the electronic structure and optical properties of CaF 2 with the self-consistent screened-exchange LDA method implemented in the highly precise full-potential linearized augmented plane wave approach. The calculated optical energy gap, 12.05 eV, is in excellent agreement with experiment (12.0±0.1 eV) and so greatly improves the LDA result (7.23 eV). The optical properties, including the imaginary part of the dielectric function and the reflectance determined ab initio with full matrix elements and no parameters, are found to be in good agreement with experiment.