Syntheses, crystal structures, energy bands, and optical characterizations of Na5Ln(MoO4)4 (Ln = Gd, Er)

Two complex molybdenum oxides, Na5Ln(MoO4)4 (Ln = Gd, Er), have been prepared under high temperature solid-state reactions. The synthesized compounds have been investigated by means of the single-crystal X-ray diffraction and spectral measurements. All of the investigated structures crystallize in space group I41/a with Z = 4; a = 11.4720(3) Å, R1 (residual factor for all date) = 0.0548 for Na5Gd(MoO4)4; a = 11.3745(3) Å, R1 (residual factor for all date) = 0.0514 for Na5Er(MoO4)4. Additionally, the calculations of band structure, density of states, dielectric constants, and refractive indices were performed with the density functional theory method for Na5Gd(MoO4)4. The results show that the solid-state compound of Na5Gd(MoO4)4 is an insulator with direct band-gap of 3.695 eV, and the calculated refractive indices is 2.063 at the static case.