Unravelling NbSe2 single crystal: First principle insights, optical properties, synthesis and X-ray diffraction profile investigation

Niobium diselenide (NbSe₂) crystals were synthesized using the chemical vapour transport (CVT) technique. The Generalized Gradient Approximation (GGA) method was used in the density functional theory (DFT) calculation. The Perdew-Burke-Ernzerhof (PBE) pseudopotential function was utilised to emphasise the structural, electrical, elastic constant, and optical characteristics of the hexagonal P6₃/mmc symmetric structured crystalline phase of NbSe₂. Additionally, the density of states (DOS) revealed that, at the Fermi level, the Nb (3d) states predominated, with the Se (5p) and Se (5 s) states playing a minor role. The band structure confirmed the crystal's metallic nature, which showed an overlap between the conduction and valence bands. Scherrer method, Williamson-Hall (WH) analysis, Size-Strain Plot (SSP), and Halder-Wagner (HW) plot utilising uniform deformation model (UDM), uniform stress deformation model (USDM), and uniform deformation energy density model (UDEDM) models were used to investigate the X-ray diffraction (XRD) profile. The crystallite size, inherent stress, strain, and energy density parameters were estimated. Optical microscopy and transmission electron microscopy (TEM) had both been used to study surface morphology.