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<p>Based on first-principles calculations combining density functional theory (DFT) and the Boltzmann transport equation, this study systematically investigates the thermoelectric properties of two-dimensional Nb<sub>2</sub>XSe<sub>2</sub> (X = B, C, N) materials. The electronic structure near the Fermi level exhibits strong hybridization between Nb d-orbitals and X/Se p-orbitals, coexisting with heterogeneous bonding characteristics—polar covalent Nb–Se bonds and delocalized ionic Nb–B/C/N bonds. Phonon transport analysis reveals that, with increasing atomic number of X, the enhanced hybridization between antibonding and bonding states elevates lattice anharmonicity, leading to an increase in the acoustic-mode Grüneisen parameter |<i>γ</i>| from 1.9 to 3.1 and a significant reduction in lattice thermal conductivity from 4.13 to 0.30&#xa0;W/(m·K). Thermoelectric optimization results demonstrate that p-type doped Nb<sub>2</sub>CSe<sub>2</sub> simultaneously achieves the maximum Seebeck coefficient (-70.4 µV·K<sup>− 1</sup>) and power factor (13.4 mW·m<sup>− 1</sup>·K<sup>− 2</sup>), yielding a peak <i>zT</i> value of 0.92 at room temperature. In contrast, the <i>zT</i> values of all three compounds under n-type doping are approximately 0.04–0.38. The realization of high <i>zT</i> values relies on low lattice thermal conductivity as the foundation, along with the synchronous enhancement of electronic transport properties to achieve a synergistic balance between electron and phonon transport.</p>

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Unraveling Thermoelectric Properties of 2D Nb2XSe2 (X = B, C, N) via First-principles Calculations

  • 期刊论文

  • 发表日期：

    2026年4月1日

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  • Shengzhao Wang,
  • Lanli Chen

摘要

Based on first-principles calculations combining density functional theory (DFT) and the Boltzmann transport equation, this study systematically investigates the thermoelectric properties of two-dimensional Nb2XSe2 (X = B, C, N) materials. The electronic structure near the Fermi level exhibits strong hybridization between Nb d-orbitals and X/Se p-orbitals, coexisting with heterogeneous bonding characteristics—polar covalent Nb–Se bonds and delocalized ionic Nb–B/C/N bonds. Phonon transport analysis reveals that, with increasing atomic number of X, the enhanced hybridization between antibonding and bonding states elevates lattice anharmonicity, leading to an increase in the acoustic-mode Grüneisen parameter |γ| from 1.9 to 3.1 and a significant reduction in lattice thermal conductivity from 4.13 to 0.30 W/(m·K). Thermoelectric optimization results demonstrate that p-type doped Nb2CSe2 simultaneously achieves the maximum Seebeck coefficient (-70.4 µV·K− 1) and power factor (13.4 mW·m− 1·K− 2), yielding a peak zT value of 0.92 at room temperature. In contrast, the zT values of all three compounds under n-type doping are approximately 0.04–0.38. The realization of high zT values relies on low lattice thermal conductivity as the foundation, along with the synchronous enhancement of electronic transport properties to achieve a synergistic balance between electron and phonon transport.