ENERGY DISPERSIONS AND BANDWIDTH IN PD 4D PHOTOEMISSION SPECTRA

Atomic and electronic structures of a Pd(111) single crystal and a pol ycrystalline Pd film have been investigated by using low-energy electr on diffraction (LEED) and photoemission spectroscopy (PES). LEED patte rns of a clean Pd(111) show a threefold symmetry, suggesting no surfac e reconstruction. Band structures of Pd(111) for k(1) along the <(Gamm a)over bar>-(M) over bar', <(Gamma)over bar>-(M) over bar, and <(Gamma )over bar>-(M) over bar symmetry lines have been determined experiment ally from angle-resolved photoemission spectroscopy measurements and c ompared to those calculated within the local-density-functional approx imation (LDA). The valence band PES spectrum of Pd film is also obtain ed and compared to the calculated 4d angular momentum projected local density of states within LDA. Experimental and LDA band structures of Pd(111) exhibit a reasonably good agreement, whereas experimental band widths are narrower than the LDA bulk bandwidths by 0.5-1 eV. Such a d iscrepancy can be improved theoretically by taking into account more l ocalized Pd surface states. Tn contrast, the calculated Pd 4d quasipar ticle spectral density by including the on-site Coulomb correlation ca nnot resolve the disagreement between PES and LDA, suggesting that the Coulomb correlation effect is not substantial in understanding PES sp ectra of Pd. [S0163-1829(97)01540-3].