Photoinitiated processes are not only important for understanding natural phenomena but they also play an undeniable role in the booming fields of renewable energy, material design and medicine. Excited state processes have traditionally been explained from a static point of view, delivering in some cases a biased, incorrect or even incomplete description of the former. The simulation of the dynamics of such processes is therefore fundamental for the quest to understand the chemical and physical mechanisms.
The purpose of this school is to introduce its participants to state-of-the-art methodologies for the simulation of the dynamics of processes in the excited state, following the evolution in time of photoinitiated reactions, one of the priority topics of this call.
The school will be focused in simulating the dynamics of complex molecules. Electronic ab initio or TD-DFT methods would be sketched for obtaining the electronic wavefunctions or densities, that would be afterwards quantum-mechanically propagated. Moreover, several approaches for the treatment of the nuclei will be also provided, from full quantum dynamics to mixed quantum-classical dynamics.

The tutorial will be organized in 6 theoretical and 5 practical sessions, the latter taking place in the computer lab. The theoretical sessions will be of 3 hours and practical sessions will last 3 hours. The school will comprise 3 didactic blocks.
The first block will have an introductory character and will offer an overview of the field. The following block will focus on mono- and multi-configurational electronic structure methods for the description of excited states. The last block will cover dynamics methodologies. See description below. The school will end with a comprehensive overview (2 hours) of state-of-the-art applications, limitations, suitabilities, future perspectives and challenges of the different static and dynamical approaches described in the school.
1st Block (11 hours): Overview of modern electronic and vibrational photochemistry. Born-Oppenheimer approximation. Ground and excited potential energy surfaces topology and light-matter interaction. Building bridges between experiment and theory: theoretical approaches to simulate steady state and transient absorption spectra. Dynamics of excited state deactivation processes.

2nd Block (12 hours): Quantum Chemical Calculations of Excited States: Mono- and Multiconfigurational Methods. CASSCF and RASSCF methods. Choice of the active space. Single vs. state-average calculations. Basis sets considerations. Introducing dynamical correlation: the CASPT2 method. CASPT2 problems and solutions. DFT. Runge-Gross theorems. This block includes 2 practical sessions of 3 hours each, comprising introductions to MOLCAS code, simulation of absorption spectra and exploration of the topography of potential energy surfaces (location of stationary points and surface crossings).

3rd Block (15 hours): Linear response TDDFT. Propagation of the electronic density. Spectra calculation. Approximation of xc-functionals. Wave Packet propagations and mixed quantum classical dynamics. Time-evolution operator, propagation. Relaxation method, filtering method. Interaction with an electric field. Correlation functions, spectra and eigenfunctions. Pump-probe spectroscopy and control. Born-Oppenheimer and Ehrenfest dynamics. Nonadiabatic dynamics, Tully's surface hopping. This block includes 3 practical sessions of 3 hours each, introducing quantum and mixed quantum classical dynamics techniques.