Influence of bonding on superconductivity in high-pressure hydrides

The recent reports on high-temperature superconductivity above 190 K in hydrogen sulfide at 200 GPa pressure, exceeding all previously discovered superconductors, has greatly invigorated interest in dense hydrogen-rich solids. Here, we investigate a possible way to optimize the critical temperature in these compounds by using first-principles linear-response calculations. We construct hypothetical alchemical atoms to smoothly interpolate between elements of the chalcogen group and study their bonding and superconducting properties. Our results show that the already remarkable critical temperatures of H₃S could be improved even further by increasing the ionic character of the relevant bonds, i.e., partially replacing sulfur with more electronegative elements.