Ab Initio Study of Complex Systems: Superconductivity in Amorphous Cu_xZr_1-x_. Electronic and Vibrational Properties.

Many materials that include copper in their composition have been found to be superconducting. However, pure copper does not superconduct at temperatures so far studied. Amorphous superconducting alloys are of particular interest because of the interplay between the disorder-driven Anderson’s localized states and the macroscopically coherent superconducting state, in principle two competing electronic arrangements. It is therefore remarkable that amorphous alloys in the Cu_xZr_1-x system have been found to be superconducting while their crystalline counterparts have not. Here we revisit superconductivity in the amorphous Cu_xZr_1-x system at various concentrations using the BCS approach as a simple mechanism to understand their properties. Ab initio DFT molecular dynamics was used, together with the undermelt-quench approach developed within our group, to generate amorphous supercells with 216 atoms. The electronic and vibrational densities of states for these structures were obtained and were used to estimate the transition temperatures of some of the specimens studied. Results will be presented and analysed and conclusions drawn.