Bonding Heterogeneity Inducing Low Lattice Thermal Conductivity and High Thermoelectric Performance in 2D CdTe₂

Abstract

materials have emerged as a broad platform for exploring promising thermoelectric materials. Motivated by the fabrication of diverse artificially designed Tebased 2D materials with high thermoelectric performance, here, we predicted 2D hexagonal CdTe and pentagonal CdTe 2 for potential thermoelectric materials, using the particle swarm optimization (PSO) method combined with density functional theory. CdTe and CdTe 2 show predicted direct/indirect band gaps of 1.82 and 1.96 eV, respectively. Chemical bonding analysis revealed that all the Te atoms in CdTe are coupled through uniform ionic bonding. CdTe 2 exhibits bonding heterogeneity, arising from weak the Cd− Te ionic bonding and strong Te−Te covalent bonding. Based on Boltzmann transport theory, we found that the bonding heterogeneity in CdTe 2 favors low lattice conductivity. The calculated lattice thermal conductivity of CdTe 2 is 0.33 Wm −1 K −1 at 300 K, which was contributed by the weaker coupling between acoustic and optical phonon modes, low group velocities of the acoustic modes, and high lattice anharmonicity. On the other hand, the occupied π* 5p , π 5p , and σ 5p bondings in Te−Te pairs significantly facilitate the electrical conductivity and enhance the Seebeck coefficient of p-type CdTe 2 . The low thermal conductivity and high power factor in CdTe 2 give rise to a high thermoelectric performance at low temperature. Our findings should encourage the exploration of 2D materials for thermoelectric applications with strong bonding heterogeneity.

Strain and thickness effects on the electronic structures of low-energy two-dimensional CdxTey phases

“…1(d)] is marginally stable as it occupies the position of 6 meV per atom above the convex hull. This observation contradicts the results in a recent report, 37 showing it on the convex hull, which might result from their consideration of an insufficient number of structures and generations in the search process. The search for low-energy phases of variable composition strongly depends on the population size, especially in the first generation.…”

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

“…This accounts for the noticeably larger Te–Te antibonding state extending from −2.3 eV up to E F , as illustrated in Figure h,i. It should be noted that strong antibonding states also appear in the Te 2 dimer of 2D CdTe 2 , which is consistent with our molecular orbital analysis. From the above discussion, it is evident that the chemical bonds transition from covalent bonding in w-InSb to s–p and p–p antibonding states in SnTe and CdTe 2 , respectively.…”

Uncovering 0D and 1D Electrides with Low Work Function in a Sc–P System

“…The total atom limit is set as 40. Consequently, we performed structure searches with fixed compositions, that is, Sc 4 P, Sc 3 P, Sc 2 P, Sc 5 P 3 , Sc 3 P 2 , ScP, ScP 2 , ScP 3 , and ScP 4 using the CALYPSO algorithm. − To evaluate the phase stability of all Sc–P compounds, the formation enthalpy per atom (Δ H f ) was calculated using the following equation normalΔ H normalf ( Sc x P y ) = H normalSc x normalP y − x H normalSc − y H normalP x + y where H denotes the enthalpy of the relaxed Sc x P y compounds, element scandium and element phosphorus. The reference phases were selected as Sc-I (0–23 GPa), Sc-II (23–76 GPa), and Sc-III (76–100 GPa) for Sc and P_ Cmca (0–4 GPa), P_ R-3m (4–10 GPa), and P_ Pm-3m (10–100 GPa) for P, respectively.…”