Why pressure induces an abrupt structural rearrangement in PdTe2 but not in PtTe2

High-pressure X-ray diffraction measurements were carried out for polymeric CdI2-type compounds MTe2 (M=Pt, Pd) to investigate if they undergo a structural phase transition under pressure as does IrTe2. Up to 27 GPa at room temperature PtTe2 does not undergo any structural phase transition. In contrast, however, an abrupt change in the inter-atomic distances occurs in PdTe2 above 15.7 GPa at room temperature, and above 5 GPa at 300 °C, but the volume vs. pressure curve exhibits no discontinuity. To account for the differences between the isostructural compounds PtTe2, PdTe2 and IrTe2, their electronic structures and bonding were analyzed on the basis of first principles electronic band structure calculations.