  This book chapter is a general introduction to photo-dynamics. An outlined
structure to the theoretical studies on classical/quantum/mixed dynamics were
described from the literature point of view. Such methods get constrained for
the practical applications due to parametrizations/computational cost. As an
alternate TDDFT-based dynamics studies are promising. we have shown that the
TDDFT calculations could be as accurate as high quality monte-carlo
calculations and the reliability of the TDDFT calculations for locating the
conical intersection through the simple ring-opening reaction of oxirane. Pros
and cons of TDDFT for photo-dynamics calculations have been presented for the
development of this fast evolving field.
