title: Computational Spectroscopy of Large Systems in Solution: The DFTB/PCM and TD-DFTB/PCM Approach.
abstract: The Density Functional Tight Binding (DFTB) and Time Dependent DFTB (TD-DFTB) methods have been coupled with the Polarizable Continuum Model (PCM) of solvation, aiming to study spectroscopic properties for large systems in condensed phases. The calculation of the ground and the excited state energies, together with the analytical gradient and Hessian of the ground state energy, have been implemented in a fully analytical and computationally effective approach. After sketching the theoretical background of both DFTB and PCM, we describe the details of both the formalism and the implementation. We report a number of examples ranging from vibrational to electronic spectroscopy, and we identify the strengths and the limitations of the DFTB/PCM method. We also evaluate DFTB as a component in a hybrid approach, together with a more refined quantum mechanical (QM) method and PCM, for the specific case of anharmonic vibrational spectra.
authors.affiliation: Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126, Pisa, Italy.|INFN Sezione di Pisa, Edificio C - Polo Fibonacci Largo B. Pontecorvo, 3-56127 Pisa, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Barone
authors.affiliation: Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126, Pisa, Italy.|INFN Sezione di Pisa, Edificio C - Polo Fibonacci Largo B. Pontecorvo, 3-56127 Pisa, Italy.
authors.forename: Ivan
authors.initials: I
authors.lastname: Carnimeo
authors.affiliation: Gaussian, Inc., 340 Quinnipiac Street Building 40, Wallingford, Connecticut 06492, United States.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Scalmani