A series of lithium rare earth polyphosphates [LiLn(PO3)4] (Ln = Tb, Ho, Yb) and their structural, optical, and electronic properties

The structural, optical, and electronic properties of a series of lithium rare earth polyphosphates [LiLn(PO3)4] [Ln = Tb(1), Ho(2), Yb(3)] have been investigated by means of single-crystal X-ray diffraction, spectroscopic measurements and calculations of energy-band structures, density of states, and optical response functions by density functional methods. These LiLn(PO3)4 systems are monoclinic with space group C2/c and Z = 4. Their unit-cell parameters decrease as the ionic radius of Ln3+ decreases (Tb3+ > Ho3+ > Yb3+). Both (PO4)3− zig-zag chains and infinite chains formed by the alternate connection of LnO8 polyhedra and LiO4 tetrahedra run parallel to the b-axis in the structure. The energy-band structures, density of states, the chemical bonds, and optical properties have been investigated by density functional methods for LiYb(PO3)4.