Tracking the electron shakedown pathway of a core-excited system using real-time TDDFT

Understanding how core-level excitations drive ultrafast electron relaxation is key to interpreting modern X-ray spectroscopies and chemical reactivity under extreme conditions. Using real-time time-dependent density functional theory (RT-TDDFT), we simulate the evolution of copper(II) chloride dihydrate (CuCl₂·2H₂O) after a 1s excitation. The explicit time propagation captures the self-consistent response of valence electrons to the transient core-hole potential, showing coherent charge redistribution and occupation oscillations on sub-femtosecond timescales. The resulting charge-transfer pathways link molecular structure to measurable spectroscopic features. This work demonstrates how first-principles time-domain simulations can connect static electronic-structure theory with time-resolved X-ray experiments to predict core-excited electron dynamics in complex materials.