Shift of indirect to direct bandgap and optical response of LaAlO3 under pressure

The structural and optoelectronic properties of LaAlO3 under pressure have been investigated for the first time using the highly accurate all electrons full potential linearized augmented plane wave method. The calculated lattice parameter at zero pressure is found in excellent agreement with the experimental results. Furthermore, with the increase in the external pressure, the lattice constant as well as bonds length decreases in accordance with the experimental results. The compound at zero pressure is an indirect bandgap semiconductor, while interestingly the indirect nature shifts to direct one with the increase of the pressure. The bonding in the material is of mixed covalent and ionic nature. In optical properties, frequency dependent parameters such as real and imaginary parts of dielectric function, refractive index, reflectivity, optical conductivity, absorption coefficient, and sumrules are calculated under pressure.

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