Modeling environment effects on spectroscopies through QM/classical models

In this perspective, an overview of the recent progress in the combination of quantum mechanical (QM) simulations of spectroscopies with classical models to include environment effects is presented. Both atomistic and continuum formulations of the classical models are reviewed together with a critical analysis of their respective pros and cons. In particular, the different strategies developed within the two families of methods to include mutual polarization effects between the QM and the classical part or to properly treat the statistical sampling are presented and discussed. Examples of applications to different types of environment are also presented to show how these hybrid approaches can be used to obtain an accurate description of electronic, vibrational and magnetic spectroscopies even when nonequilibrium, heterogeneities, and/or specific and bulk effects are in play.