Introduction
Reliable simulations or prediction of dynamic, spectroscopic, and thermodynamic properties of real systems that contain light atoms, where nuclear quantum effects are important at low or room temperatures, present challenging frontiers in both quantum molecular dynamics and electronic structure theory.
When the time scales of electronic and nuclear dynamics are separable, the state-of-art wavefunction-based approach or DFT with accurate functional faithfully helps yield the single (ground) electronic state potential energy surface or force field. Modern semiclassical dynamics, phase space quantum dynamics, or time-dependent basis set methods provide practical tools for studying the vibrational spectrum, thermal reaction rate, vibrational energy relaxation rate, thermal conductivity, isobaric heat capacity, thermal expansion coefficient, isothermal compressibility, and so forth. On the other hand, in many light-driven, intersystem crossing, or electron/charge/spin transfer processes in chemical, biological, or materials systems, electronic motion and nuclear motion can be strongly coupled, and nonadiabatic transitions play an important role. Recent advances in time-dependent DFT (TD-DFT), multi-state DFT (MS-DFT) or multireference wavefunction-based approaches (e.g., CASSCF, MRPT, MRCI, CASPT2, iCI, iVI) reliably describe multi electronic states and nonadiabatic couplings/spin–orbit couplings between different states involved in such cases. Significant progress has been made by surface hopping, symmetrical quasi-classical dynamics with the mapping Hamiltonian model, nonadiabatic field, exact factorization, multi-configuration-based approaches for studying the electronic population and coherence, time-resolved spectroscopy, carrier mobility, nonadiabatic reaction rate, and other properties in large systems in gas phase and condensed phase.
Despite the aforementioned advances in the context of ab initio quantum molecular dynamics, it remains challenging to economically generate the accurate description of conical intersections, spin–orbit couplings, and long time nonequilibrium dynamics in complex systems with multi scales in space and time. The efficient integration of electronic structure and quantum dynamics for larger systems involve scalable strategies, such as automatically-adaptive time-step, quantum embedding, fragmentation-based techniques, enhanced sampling approaches for consistent initial condition sampling as well as for faithful observable evaluation, and robust artificial intelligence (AI) methods with rational design.
The proposed summer school will bring together experts in electronic structure theory, quantum dynamics, and software development in order to promote the synergy between these frontiers of theoretical chemistry. If successful, it probably opens the new avenue to the joint research for the next generation of ab initio quantum molecular dynamics.
