Octopus is a pseudopotential real-space package aimed at the simulation of the electron-ion dynamics of one-, two-, and three-dimensional ?nite systems subject to time-dependent electromagnetic ?elds.
All quantities are expanded in a regular mesh in real space, and the simulations are performed in real time. Note also that in the real-space method there is only one convergence parameter, namely the grid-spacing, and that decreasing the grid spacing always improves the result.
The program has been successfully used to calculate linear and non-linear absorption spectra, harmonic spectra, laser induced fragmentation, etc. of a variety of systems. The fundamentals of DFT and TDDFT can be found, e.g., in the books [1]and [2]. All information about the octopus package can be found in its homepage, http://www.tddft.org/programs/octopus/, and in the articles [3]and [4].
