First principles simulations of transition metals for diodes: challenges and approaches to overcome inaccuracies in calculations

The electronic, optical, and mechanical properties of transition metals belonging to groups 4B (Cr, Mo, and W), 8B (Ni, Pd, and Pt), and 9B (Cu, Ag, and Au) were investigated using Density Functional Theory (DFT). Three exchange-correlation functionals PBE, R²SCAN, and HSE06 were used and compared to evaluate their capability in prediction performance based on different physical properties. The results obtained from the density of states (DOS) calculations revealed a strong agreement between PBE and R²SCAN, while HSE06 introduced significant shifts in the valence and conduction regions due to the inclusion of the exact Hartree-Fock exchange. The optical properties of these metals highlighted that PBE and R²SCAN have reproduced the experimental curves with higher accuracy for metals with filled or nearly filled d bands, whereas HSE06 performs better for metals with more localized d states. The mechanical properties were considered in terms of Young's modulus; the outcomes revealed that metals which did not exhibit electronic d promotions possess higher values of the elastic modulus. This work highlights how electronic structure prediction, bond hybridization, and electronic promotion determine the properties of the considered metallic elements, highlighting the strengths and weaknesses of the three computational approaches and suggesting guidelines for obtaining reliable simulations for pure metal systems.