Exploring Excited-State Electronic Structure, Spectroscopy, and Nonadiabatic Dynamics with CP2K's Multifaceted Approach.

The CP2K software package provides a comprehensive suite of density functional theory-based methods for studying excited states and spectroscopic properties of molecular and periodic systems. In this review, we present recent developments and applications of several complementary approaches implemented in CP2K, including linear-response time-dependent (TD) and time-independent density functional perturbation theory (DFPT), delta self-consistent field (ΔSCF), and real-time TDDFT (RT-TDDFT). Nonadiabatic molecular dynamics (NAMD) capabilities are integrated with ΔSCF and TD-DFPT methods, in addition to Ehrenfest dynamics based on RT-TDDFT, enabling detailed investigations of photochemical processes and the excited-state dynamics in gas and condensed phase systems. Applications demonstrating the versatility of these methods include studies on solvated molecules, surface-bound photosensitizers, and two-dimensional materials. Spectroscopic methods encompass, e.g., ultraviolet-visible absorption, electronic circular dichroism, Raman (optical activity), infrared absorption, and vibrational circular dichroism spectra. We demonstrate that CP2K provides a unique and powerful toolkit for studying a wide range of excited-state phenomena in complex molecular and extended (periodic) systems.