Electronic transitions for a fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles: Linear and corrected linear response regimes

Tommaso Giovannini; Rosario Roberto Riso; Matteo Ambrosetti; Alessandra Puglisi; Chiara Cappelli

doi:10.1063/1.5121396

Electronic transitions for a fully polarizable QM/MM approach based on fluctuating charges and fluctuating dipoles: Linear and corrected linear response regimes

J Chem Phys. 2019 Nov 7;151(17):174104. doi: 10.1063/1.5121396.

Authors

Tommaso Giovannini¹, Rosario Roberto Riso², Matteo Ambrosetti², Alessandra Puglisi², Chiara Cappelli²

Affiliations

¹ Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
² Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy.

PMID: 31703497
DOI: 10.1063/1.5121396

Abstract

The fully polarizable Quantum Mechanics/Molecular Mechanics (QM/MM) approach based on fluctuating charges and fluctuating dipoles, named QM/FQFμ [T. Giovannini et al., J. Chem. Theory Comput. 15, 2233 (2019)], is extended to the calculation of vertical excitation energies of solvated molecular systems. Excitation energies are defined within two different solvation regimes, i.e., linear response (LR), where the response of the MM portion is adjusted to the QM transition density, and corrected-Linear Response (cLR) in which the MM response is adjusted to the relaxed QM density, thus being able to account for charge equilibration in the excited state. The model, which is specified in terms of three physical parameters (electronegativity, chemical hardness, and polarizability) is applied to vacuo-to-water solvatochromic shifts of aqueous solutions of para-nitroaniline, pyridine, and pyrimidine. The results show a good agreement with their experimental counterparts, thus highlighting the potentialities of this approach.