The structural, electronic and dynamical investigations of NdMn₂O₅ and La₂CoMnO₆ for optoelectronic applications: A first principles study

The first principles simulation is performed to study the structural, electronic and dynamical properties of single perovskite NdMn₂O₅ and double perovskite La₂CoMnO₆. Their lattice constants for optimized orthorhombic phases are calculated from the structural properties using Conjugate Gradient method. The calculated electronic energy band gaps for NdMn₂O₅ (1.07 eV) and La₂CoMnO₆ (0.95 eV) are found to be suitable for optoelectronic applications. The vibrational properties are determined and compared using harmonic approximation for the supercell and semi empirical methods to explore stability of the compounds, and their modes of vibrations. The vibrational modes are characterized in infrared (IR) and Raman regions between the frequencies ranging 59 to 699 cm⁻¹. These modes are discussed to analyze motion of the individual atom in complex structures of NdMn₂O₅ and double perovskite La₂CoMnO₆. Slater type stretching modes are observed at frequency 550 cm⁻¹ and 512 cm⁻¹ of NdMn₂O₅ and La₂CoMnO₆, respectively.