Structural, electronic and thermodynamic properties of bulk and surfaces of terbium dioxide (TbO₂)

This contribution reports a comprehensive investigation into the structural, electronic and thermal properties of bulk and surface terbium dioxide (TbO₂); a material that enjoys wide spectra of catalytic and optical applications. Our calculated lattice dimension of 5.36 Å agrees well with the corresponding experimental value at 5.22 Å. Density of states configuration of the bulk structure exhibits a semiconducting nature. Thermo-mechanical properties of bulk TbO₂ were obtained based on the quasi-harmonic approximation formalism. Heat capacities, thermal expansions and bulk modulus of the bulk TbO₂ were obtained under a wide range of temperatures and pressures. The dependency of these properties on operational pressure is very evident. Cleaving bulk terbium dioxide affords six distinct terminations. Bader's charge distribution analysis for the bulk and the surfaces portrays an ionic character for Tb-O bonds. In an analogy to the well-established finding pertinent to stoichiometric CeO₂ surfaces, the (111):Tb surface appears to be the thermodynamically most stable configuration in the nearness of the lean-limit of the oxygen chemical potential. For the corresponding non-stoichiometric structures, we find that, the (111):O + 1V_O surface is the most stable configuration across all values of accessible oxygen chemical potentials. The presence of an oxygen vacant site in this surface is expected to enable potent catalytic-assisted reactions, most notably production of hydrogen from water.