Empirical electron-phonon coupling constants and anisotropic electrical resistivity in hcp metals

The Fermi-surface density of states N(0) and Drude-plasma-frequency tensor (Ωₚ²{)}_{{α}{β}}=4π{e}²$N(0)〈${v}_{{α}}v_β〉 are calculated for 14 metallic elements with hcp structures. By comparison with measured anisotropic resistivity components ρ_⊥ and ρ?, electron-phonon coupling constants are extracted. The resulting values of λₜᵣ compare reasonably well with {λ} from Tc for the ten superconducting elements and provide new information on electron-phonon coupling for the four that are not. In particular, λₜᵣ for Mg is sufficiently low as to discourage a further search for superconductivity, whereas λₜᵣ for Sc and Y is sufficiently high (0.5--0.6) to require spin-fluctuation suppression of Tc and motivate a low-T search for exotic superconductivity. Co is found to have very weak electron-phonon coupling in the majority-spin band and much stronger specific-heat enhancement in the minority-spin band. The anisotropy ρzz/ρₓₓ=ρ?/ρ_⊥ is moderately well accounted for by the anisotropy of the Drude plasma frequency (Ωₚ²{)}ₓₓ$/(${{Ω}}ₚ²)zz =〈vₓ²〉/〈vz²〉, except for the sp elements, which have significant scattering anisotropy (λzz/λₓₓ{≠}1). A systematic onset of ``resistivity saturation'' (signifying a breakdown of Boltzmann theory) is found when the mean free path l{≤}10 A{}. The onset occurs at a variable value 40<{ρ}<160 {μ}{Ω} cm.