We present an implementation of a time-dependent semiempirical method (INDO/S) in NWChem using real-time (RT) propagation to address, in principle, the entire spectrum of valence electronic excitations. Adopting this model, we study the UV/vis spectra of medium-sized systems such as P3B2 and f-coronene, and in addition much larger systems such as ubiquitin in the gas phase and the betanin chromophore in the presence of two explicit solvents (water and methanol). RT-INDO/S provides qualitatively and often quantitatively accurate results when compared with RT- TDDFT or experimental spectra. Even though we only consider the INDO/S Hamiltonian in this work, our implementation provides a framework for performing electron dynamics in large systems using semiempirical Hartree-Fock Hamiltonians in general.
Bibliographical noteFunding Information:
*(N.G.) E-mail: email@example.com. *(L.G.) E-mail: firstname.lastname@example.org. *(C.J.C.) E-mail: email@example.com. ORCID Soumen Ghosh: 0000-0003-0850-4855 Laura Gagliardi: 0000-0001-5227-1396 Christopher J. Cramer: 0000-0001-5048-1859 Funding This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences and the Office of Advanced Scientific Computing Research through the Scientific Discovery through Advanced Computing (SciDAC) program under Award Nos. DE-SC0008666 (S.G., C.J.C., and L.G.) and KC-030106062653 (A.A. and N.G.). The research was performed using The Minnesota Supercomputing Institute (MSI) at the University of Minnesota and EMSL, a DOE Office of Science User Facility sponsored by the Office of Biological and Environmental Research and located at the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle Memorial Institute for the United States Department of Energy under DOE Contract No. DE-AC05-76RL1830. Notes The authors declare no competing financial interest.