First-Principles Investigation of the Chemical Bonding, Electronic Structure and Superconducting Properties of Vanadium Nitride with Insights into Thermoelectric and Spin Hall Effects
摘要
In this paper, we present a comprehensive first-principles investigation of the electronic structure of vanadium nitride (VN) using density functional theory. To characterize the chemical bonding, we employ multiple complementary approaches: Electron localization function (ELF), crystal orbital Hamilton population (COHP), crystal orbital bond index (COBI) and Löwdin charge analysis. These results collectively demonstrate a predominantly ionic bonding between vanadium (V) and nitrogen (N) atoms. Analysis of the band structure, density of states (DOS), and Fermi surface topology confirms the metallic character of VN. The phonon spectrum confirms dynamical stability, with no imaginary frequencies across the Brillouin zone. The calculated superconducting critical temperature (Tc), based on the McMillan–Allen–Dynes formula, agrees well with experiment, supporting the conventional phonon-mediated BCS mechanism in VN. Thermoelectric calculations reveal that VN exhibits exceptional electrical conductivity (σ/τ ≈ 6.1 × 1020 Ω−1.m− 1.s− 1, combined with intriguing carrier-type switching behavior. Notably, the spin Hall conductivity (SHC) of the VN system is approximately 5000 (ħ/e)Ω−1.cm− 1, significantly exceeding that of noble metals such as Pt and other 4d/5d transition metals. This combination of high charge/spin conductivity and thermoelectric responsiveness positions VN as a promising candidate for spintronic-thermoelectric hybrid devices.