Mechanisms for the 200 K transition in TiSe₂: A measurement of the specific heat

We present specific heat measurements on TiSe2 from 1.3 to 300 K that show a peak at the 200 K transition, where previous data show that the hexagonal a and c axis double. The specific heat shows the transition to be second order, in agreement with other measurements. The anomaly is small, ∼ 1.15 J/mole K out of 65 J/mole K total, and is consistent with models that suggest the transition is electronically driven. We are unable, however, to rule out the possibility of a phonon instability unconnected with the presence of carriers. © 1978.