Band Jahn–Teller effects in Rh2TMSn full Heusler compounds

• Five among six Rh2TMSn Heusler compounds show structural instability.
• The instability can be explained by the band Jahn–Teller effect.
• The compounds can be categorized into two groups according to their DOS at EF.
• Rh2MnSn has the largest tetragonal distortions with c/a = 1.9.

Electronic structures of Rh2TMSn (TM = Cr, Mn, Fe, Co, Ni and Cu) full Heusler compounds are calculated by the state-of-the-art electronic structure codes with the local density approximation aiming to understand the structure instability microscopically. The instability of the compounds can be explained by the band Jahn–Teller effect. The compounds can be categorized into two groups: In the first group, the density of states at the Fermi level are contributed mainly from Rh, while in the rest, both the Rh and TM atoms contribute. The high density of states at the Fermi level of the first group compounds may be smoothed and the highly symmetric phase is stable as found in experiments. The compounds in the second group tetragonally distort according to our calculation and was found in the experiments.