Systematic study on crystal structures in tetragonal RB2C2 (R=rare earth) compounds

Detailed crystal structures of the tetragonal RB2C2 (R=La, Ce, Pr, Nd, Tb, Dy, Ho, Er, Tm and Lu) compounds which include the antiferroquadrupolar ord ering materials, DyB2C2 and HoB2C2, have been investigated by neutron powde r diffraction technique. RB2C2 are crystallised in the same LaB2C2 type cry stal structure with P4/mbm symmetry. The structure of the B-C network which consists of non-regular squares and octagons are nearly the same in the sy stem except slight rotation as rare earth atoms become heavier.