Temperature dependence of infrared-active phonons in CaTiO3:: A combined spectroscopic and first-principles study -: art. no. 224303

Spectroscopic studies involving dielectric, submillimeter, infrared, and Raman measurements were performed on a CaTiO3 single crystal, covering a broad spectral range (static to 10 THz) at temperatures from 6 to 300 K. The results show mode softening characteristic of an incipient ferroelectric with T(c)approximate to-105 K. A signature of the soft mode is seen in the Raman spectra, even though the soft modes are not Raman active to first order. First-principles calculations were used to identify the phonons responsible for the spectral features. Many of the major features are due to phonons in orthorhombic CaTiO3 that are associated with zone-boundary phonons of the cubic perovskite phase.