Description
Over the past decades, experiments probing the X-ray-induced electron dynamics of various atomic/molecular systems in complex environments have provided mounting evidence that these dynamics occur on timescales of tens to hundreds of attoseconds.$^{1,}$$^{2,}$$^3$ In stark contrast to the wealth of empirical evidence, a fully ab initio wavefunction-based description of the underlying dynamics remains elusive.
To make progress on this front, we revisit the floating spherical Gaussian orbital (FSGO) model,$^4$ one of the simplest ab initio electronic structure methods. By combining this wave function parametrization with the time-dependent variational principle,$^5$ we develop a flexible and scalable computational method for simulating X-ray-induced ultrafast electron dynamics in complex environments. Here, we present the current state of development, highlighting key milestones achieved to date and outlining remaining challenges.
