  We apply a three-dimensional (3D) implementation of the time-dependent
restricted-active-space self-consistent-field (TD-RASSCF) method to investigate
effects of electron correlation in the ground state of Be as well as in its
photoionization dynamics by short XUV pulses, including time-delay in
photoionization. First, we obtain the ground state by propagation in imaginary
time. We show that the flexibility of the TD-RASSCF on the choice of the active
orbital space makes it possible to consider only relevant active space
orbitals, facilitating the convergence to the ground state compared to the
multiconfigurational time-dependent Hartree-Fock method, used as a benchmark to
show the accuracy and efficiency of TD-RASSCF. Second, we solve the equations
of motion to compute photoelectron spectra of Be after interacting with a short
linearly polarized XUV laser pulse. We compare the spectra for different RAS
schemes, and in this way we identify the orbital spaces that are relevant for
an accurate description of the photoelectron spectra. Finally, we investigate
the effects of electron correlation on the magnitude of the relative time-delay
in the photoionization process into two different ionic channels. One channel,
the ground state channel in the ion, is accessible without electron
correlation. The other channel is only accessible when including electron
correlation. The time-delay is highly sensitivity to the choice of the active
space, and hence to the account of electron-electron correlation.
