New methods for non-linear spectroscopy of molecules in complex environments by combination of coupled-cluster and polarizable embedding approaches

University Of Southern California, Los Angeles CA

Investigators

Abstract

Anna Krylov of the University of Southern California is supported by an award from the Chemical Theory, Models and Computational Methods program to develop robust and accurate theoretical methods and computational tools for modeling properties of molecules when they interact with light. This award is cofunded by the Computational and Data-Enabled Science and Engineering program in the Division of Advanced Cyberinfrastructure. Krylov and her research group are interested in properties known as non-linear optical (NLO) properties. NLO properties are exploited in novel technologies such as microfabrication, 3D optical data storage and nanolithography, ultra-fast electro-optic modulation and switching, bioimaging, photodynamic therapies, and a variety of other nano-bio-photonics applications. The new tools for interpretation of experimental spectra and for the in silico design of new materials with properties matching particular application are expected to impact both fundamental and applied research (such as bioimaging and molecular electronics) on NLO properties. Computer software generated from this research are made available to the broader research community through the widely-used Q-Chem and Spartan package. Once mature, the software is distributed as open-source code. The emphasis of this research is on open-shell species and molecules in complex environments. The proposed developments capitalize on the work conducted in the previous funding period, which included developing formalisms and implementing calculations of electronic factors for two-photon absorption (2PA) and static and dynamic polarizabilities within the coupled-cluster (CC) and equation-of-motion (EOM) family of methods. The main thrust the current work is to develop the formalisms and codes: (i) to include the effect of the environment (solvent, molecular solids, proteins) via the Effective Fragment Potential method; and (ii) for higher-order NLO properties within the EOM-CC framework, such as three-photon absorption moments and hyperpolarizabilities. The planned applications of the new methods include investigations of fundamental aspects of non-linear spectroscopy, such as: (i) the extent of (non)-locality of NLO properties and the convergence of these properties computed within polarizable embedding schemes with respect to the size of the QM region; (ii) the relative importance of the electrostatic perturbation and polarization response of the solvent versus the contribution from delocalized excited states (such as charge transfer to solvent states); and (iii) the effect of electron correlation on NLO properties, with an emphasis on open-shell systems.will be distributed as open source, similarly to our tensor library and other Q-CHEM modules. Professor Krylov is an active contributor to the Women in Science and Engineering program at USC and beyond. She continues to maintain and develop the ??Women in Theoretical and Computational Chemistry, Material Science, and Biochemistry?? webpage, promoting research by women in these areas.