Effect of disorder on the electronic structure of palladium

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Abstract
We have studied the effect of disorder on the electronic structure of palladium using linear muffin-tin orbitals (LMTO) –recursion and LMTO–coherent-potential-approximation (CPA) techniques. Disorder is simulated by moving atoms, via the Metropolis Monte Carlo method, from their crystalline positions, as well as by putting in vacancies. The electronic density of states (DOS) is calculated for varying degrees of positional disorder and vacancy concentrations. The peaked structure of the DOS at the Fermi energy is found to survive large vacancy concentrations (∼6%) as long as the fcc crystal structure is maintained or only weakly perturbed. Thus, some amount of positional disorder is essential in reducing the DOS at the Fermi level to the extent that the spin fluctuations can be suppressed to render the system superconducting. We argue, as well as present evidence to the effect, that while positional disorder can lower the DOS at the Fermi level and hence the tendency to magnetic ordering, the electron-phonon coupling remains nearly as strong as in pure crystalline palladium, thus explaining the observed superconductivity in irradiated films of palladium reported by Stritzker [Phys. Rev. Lett. 42, 1769 (1979)].