  In this work we present a four component relativistic theoretical
investigation of the trihalides of lutetium and lawrencium, LuX3, LrX3 (X= F,
Cl, Br, I) respectively using density functional theory (DFT) with different
density functional and a geometrical optimisation procedure as implemented in
DIRAC-package. The results show the trend of bonding from lighter to the
heavier halide atoms and between 4f/5f atoms Lu and Lr.
