Electron–phonon interaction in disordered CaAl2−xSix alloy

The electronic structure, phonon spectra and electron–phonon (EP) interaction in disordered CaAl2−xSix alloy are calculated within the virtual crystal approximation (VCA) by using the full-potential, density-functional-based method. The calculated density of states at the Fermi level does not display monotonically variation with the composition x. With the increase of composition x, there is the overall tendency of increase of phonon frequency except B1g soft mode which becomes softer. The electron–phonon coupling strength λ and the transition temperature Tc of superconductivity in these compounds have been evaluated. By comparing the calculated results respective for the in-plane disordered and the in-plane ordered CaAlSi compounds with the experimental data, we can conclude that the distribution of Al/Si is probably ordering for CaAlSi.