Large-scale first principles configuration interaction calculations of optical absorption in aluminum clusters

摘要: We report the linear optical absorption spectra of aluminum clusters Al$_{n}$ (n=2--5) involving valence transitions, computed using large-scale all-electron configuration interaction (CI) methodology. Several low-lying isomers each cluster were considered, and their geometries optimized at coupled-cluster singles doubles (CCSD) level theory. With these ground-state geometries, excited states different multi-reference singles-doubles configuration-interaction (MRSDCI) approach, which includes electron correlation effects a sophisticated level. These CI wave functions used to compute transition dipole matrix elements connecting ground various clusters, thus photoabsorption spectra. The convergence our results with respect basis sets, size expansion, was carefully examined. Our found be significantly as compared those obtained time-dependent density functional theory (TDDFT) [Deshpande \textit{et al. Phys. Rev. B}, 2003, \textbf{68}, 035428]. When available experimental data for Al$_{2}$ Al$_{3}$, are in very good agreement far important peak positions concerned. The contribution configurations many body wavefunction suggests that most cases excitations involved collective, plasmonic nature.