arXiv subjects
Publications and source records attributed to Bo Zhou.
We determine the minimum sum--connectivity index of bicyclic graphs with $n$ vertices and matching number $m$, where $2\le m\le \lfloor\frac{n}{2}\rfloor$, the minimum and the second minimum, as well as the maximum and the second maximum sum--connectivity indices of bicyclic graphs with $n\ge 5$ vertices. The extremal graphs are characterized.
We introduce a new method for simulating photoemission spectra from bulk crystals in the ultra-violet energy range, within a three-step model. Our method explicitly accounts for transmission and matrix-element effects, as calculated from state-of-the-art plane-wave pseudopotential techniques within density-functional theory. Transmission effects, in particular, are included by extending to the present problem a technique previously employed with success to deal with ballistic conductance in metal nanowires. The spectra calculated for normal emission in Cu(001) and Cu(111) are in fair agreement with previous theoretical results and with experiments, including a newly determined spectrum. The residual discrepancies between our results and the latter are mainly due to the well-known deficiencies of density-functional theory in accounting for correlation effects in quasi-particle spectra. A significant improvement is obtained by the LDA+U method. Further improvements are obtained by including surface-optics corrections, as described by Snell's law and Fresnel's equations.