Quantum fluid dynamics from density-functional theory - art. no. 022506

A partial-differential eigenvalue equation for the density displacement fie lds associated with electronic excitations is derived in the framework of d ensity-functional theory. Our quantum fluid-dynamical approach is based on a variational principle and the Kohn-Sham ground-state energy functional, u sing only the occupied Kohn-Sham orbitals. It allows for an intuitive inter pretation of electronic excitations in terms of intrinsic local currents th at obey a continuity equation. We demonstrate the capabilities of this none mpirical approach by calculating the photoabsorption spectra of small sodiu m clusters. The quantitative agreement between theoretical and experimental spectra shows that even for the smallest clusters, the resonances observed experimentally at low temperatures can be interpreted in terms of density vibrations.