First-principles study on iron-pnictide superconductors Ca(Fe1-xCox)2As2

The electronic structure, lattice dynamics, and electron-phonon (e-ph) coupling constants lambda for the superconducting Ca(Fe1-xCox)(2)As-2 (x=0.075, 0.1) are obtained by first-principles nonmagnetic calculations using norm-conserving pseudopotentials within virtual-crystal approximation treatment. Combined with the e-ph coupling constant lambda for vicinity of collapsed tetragonal phase of CaFe2As2, we show that although the obtained lambda cannot account for the high superconducting transition temperatures T-c, they are almost a factor of two larger than that estimated in early calculations for that of vicinity of collapsed tetragonal phase of CaFe2As2. We confirm that superconductivity in Ca(Fe1-xCox)(2)As-2 is not primarily phonon mediated. Nevertheless, the e-ph interactions are strong enough to be not negligible to investigate the superconductivity. Furthermore, we conjecture that Ca(Fe1-xMnx)(2)As-2 or CaMn2As2 serial compounds may be potential new e-ph superconductors or unconventional manganese pnictide superconductors. (C) 2012 Elsevier Ltd. All rights reserved.