Theoretical Study of Phonon Dispersion of Lanthanum Aluminate in Terahertz Frequency

The phonon dispersion spectrum, eigenvector and lattice vibration frequency of cubic crystalline lanthanum aluminate (LaAlO 3 ) are studied by density functional theory (DFT). The effects of lattice constant, K-point selection and kinetic-energy cutoff ( E cut ) on the calculation accuracy are discussed. The vertical parallel relationship between the phonon propagating wave vector and the atomic vibration direction is analyzed to obtain the frequency of the LaAlO 3 transverse (TO)/longitudinal (LO) optical phonon. The comparison results of the first-principles calculation software Materials Studio, the open source component package ABINIT, and he open source component package Quantum Espresso show that the calculation accuracy depends on the convergence analysis and the approximation method adopted in the calculation process.