Combined experimental and first-principles investigation of the delafossite structure AgCoO2

Motivated by the need for more detailed knowledge of its physical properties, we present first-principle investigations of the structural, electronic, dielectric, and dynamical properties of the bulk delafossite AgCoO2. The calculated crystallographic parameters show a good consistency with those determined experimentally. Within the electronic structure analysis, AgCoO2 shows a semiconducting comportment with an optical bandgap of 1.31 eV. Indeed, the photo-electrochemical study shows a p-type comportment with a valence band edge 5.25 eV below vacuum. Unlike perovskites ferroelectrics, the computed effective charges are in the same order of magnitude as their corresponding ionic values. The calculated zone-center phonon modes allowed the assignment of our experimental infrared and Raman spectra. Finally, the inspection of the full phonon dispersion spectrum, with different ionic contributions, gives a sublime interpretation of the vibrational properties of AgCoO2.