The simulated vibrational spectra of HfO2 polymorphs

The Raman and infrared (IR) spectra of HfO2 polymorphs are simulated within the framework of density functional perturbation theory. The joint lattice-dynamical model treatment of the monoclinic, orthorhombic-I, orthorhombic-II and tetragonal-polymorphs of HfO2 is conducted with an emphasis on the evolution of their vibrational spectra. Our method is based upon the local density approximation with Hartwigsen-Goedecker-Hutter-type pseudopotentials and it gives a precise description of the phonon energies in these polymorphs with small deviations relative to the available experimental data. The simulated Raman spectra of the orthorhombic-I and II HfO2 are consistent with the data from high-pressure experiments, which indicates that these samples are well crystallized and randomly oriented. Rigid assignments of all the Raman peaks of these four polymorphs are obtained. Further, the simulated IR spectra of these four polymorphs are firstly presented, and the characteristics of these spectra are obtained, which provide potential ways to identify these phases in production environments.