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

Abstract

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 (κ 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 CdTe 2 (CdSe 2 ) 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 Gruneisen parameter. Furthermore, the antibonding states in CdTe 2 , 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 κ L . Moreover, by combining the reasonably high power factor of CdTe 2 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 CdTe 2 , 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.

High throughput screening of semiconductors with low lattice thermal transport induced by long-range interactions

“…It is reported that the dimeric anti-bonding p–p hybridization has an obvious contribution to the enhancement of lattice anharmonicity by weakening the interaction of the dimer with surrounding atoms. 35 The strongly covalently bonded dimer can also result in soft phonon modes by collective vibration. 36 Fig.…”