Remarkably Weakened Atomic Bonds from Dimeric Antibonding Hybridization and Enhanced Thermoelectric Performance of CdTe2

Interatomic antibonding states are commonly linked to a reduced bonding strength and lattice anharmonicity, both of which play a crucial role in determining the heat transport properties of crystalline solids. However, there is still a need for a comprehensive understanding of their specific relevance in order to design materials with significant control over lattice thermal conductivity (kappa(L)). Herein, the nature of the antibonding state and its influence on the chemical bonds and anharmonicity in three types of w-InSb (w-InAs), SnTe (SnSe), and CdTe2 (CdSe2) compounds are studied. We show that in comparison to the strong bonding states observed in w-InSb, occupied Sn-Te antibonding states in SnTe originate from the Sn-5s and Te-5p electrons. This bonding behavior results in enhanced lattice anharmonicity, which is characterized by a large Gr & uuml;neisen parameter. Furthermore, the antibonding states in CdTe2, caused by the presence of Te-2 dimers, significantly weaken the heat transport-dominant Cd-Te bonds. As a consequence, this leads to larger bond lengths, smaller interatomic force constants, and lower Debye temperatures, contributing to a large suppression of kappa(L). Moreover, by combining the reasonably high power factor of CdTe2 that arises from its multivalley band characteristics, we find remarkably high ZTs of 2.5 and 2.4 at 500 K for p-type and n-type CdTe2, respectively. Overall, this work enhances our understanding of the relationship between antibonding states, chemical bonds, and lattice thermal conductivity, and also establishes a simplified descriptor for searching high-performance thermoelectric materials.

Automated summary

This study investigates the influence of interatomic antibonding states on chemical bonds and lattice thermal conductivity. The findings enhance our understanding of this relationship and provide a simplified descriptor for searching high-performance thermoelectric materials.