Pressure induced superconductivity and electronic structure properties of scandium hydrides using first principles calculations

The electronic, vibrational and superconducting properties of scandium hydrides (ScH₂ and ScH₃) under pressure were studied using first-principles calculations. The results indicate that ScH₂ and ScH₃ are dynamically stable in the pressure ranges of 0-85 GPa and 46-80 GPa, respectively. The superconducting properties of ScH₂ and ScH₃ were investigated by employing Bardeen-Cooper-Schrieffer (BCS) theory, and this shows that the superconducting temperature of ScH₂ initially increases exponentially and then reaches a maximum value of about 38.11 K at 30 GPa, while it remains constant under further compression. However, the superconducting behavior of ScH₃ is not obvious under low pressure (P < 46 GPa), and it almost disappears under higher pressure, in agreement with experimental observations. Analysis of the energy band structures demonstrates that the distinct superconducting behaviors of ScH₂ and ScH₃ are related to the hybridization between the s-state of the H atom and the d-state of the Sc atom. The superconducting behavior of ScH₂ follows the variation of the hybridization between the H_O-s state and Sc-d state, while for ScH₃, it is found that there is no density of states observed for H_T or H_O when the pressure is above 46 GPa. Analysis of the electronic structure of ScH₂ was also performed to allow for further comprehension of the metallic behavior of ScH₂ under pressure. This work may offer help to understand the mechanism of pressure-induced superconductivity in metal-hydride systems.