Vibrational effects on SrTiO₃Ti 1s absorption spectra studied using first-principles methods

Abstract

We analyze the vibrational effects on the Ti 1s excited states in cubic SrTiO3 and related pre-edge x-ray absorption fine structure using first-principles methods. Ground-state, total-energy and electron–core hole Bethe–Salpeter calculations are performed for different atomic configurations related to eg-symmetry distortions of SrTiO3. From these, we can obtain normal-mode gradients of the electronic excited-state energy, i.e., of the excited-state Born–Oppenheimer surface. This yields the corresponding electron–phonon coupling coefficients that allow us to predict the spectral broadening induced by those vibrational modes.