Open-ended formulation of self-consistent field response theory with the polarizable continuum model for solvation

摘要

The study of high-order absorption properties of molecules is a field of growing importance. Quantumchemicalstudies can help design chromophores with desirable characteristics. Given that most experimentsare performed in solution, it is important to devise a cost-effective strategy to include solvation effects inquantum-chemical studies of these properties. We here present an open-ended formulation of selfconsistentfield (SCF) response theory for a molecular solute coupled to a polarizable continuum model(PCM) description of the solvent. Our formulation relies on the open-ended, density matrix-basedquasienergy formulation of SCF response theory of Thorvaldsen, et al., [J. Chem. Phys., 2008, 129, 214108]and the variational formulation of the PCM, as presented by Lipparini et al., [J. Chem. Phys., 2010, 133,014106]. Within the PCM approach to solvation, the mutual solute–solvent polarization is represented bymeans of an apparent surface charge (ASC) spread over the molecular cavity defining the solute–solventboundary. In the variational formulation, the ASC is an independent, variational degree of freedom. Thisallows us to formulate response theory for molecular solutes in the fixed-cavity approximation up toarbitrary order and with arbitrary perturbation operators. For electric dipole perturbations, pole and residueanalyses of the response functions naturally lead to the identification of excitation energies and transitionmoments. We document the implementation of this approach in the Dalton program package using arecently developed open-ended response code and the PCMSolver libraries and present results for one-,two-, three-, four- and five-photon absorption processes of three small molecules in solution.