Computing Excited\nStates of Very Large Systems with\nRange-Separated Hybrid Functionals and the Exact Integral Simplified\nTime-Dependent Density Functional Theory (XsTD-DFT)

Simplified quantum chemistry (sQC)\nmethods can routinely\ncompute\nexcited states for very large systems in an “all-atom”\nfashion. They are viable alternatives to regular multiscale schemes.\nsQC methods have the advantage of accounting explicitly for all of\nthe environment at a quantum mechanical (QM) level. The treatment\nof charge-transfer states is now improved by the native implementation\nof range-separated hybrid (RSH) exchange-correlation functionals into\nthe eXact integral simplified time-dependent density functional theory\n(XsTD-DFT). After the RSH XsTD-DFT/TDA scheme was benchmarked, XsTD-DFT(/TDA)\nultraviolet/visible absorption, circular dichroism (CD), and/or two-photon\nabsorption (2PA) spectra were directly compared to the results of\nexperiments for four challenging and increasingly large systems: eYFP\nmodel system, Λ-shaped multimodular D−π–A−π–D′−π–A−π–D\nchromophore, mixed donor/acceptor ligand Pd(II) double cage [3BF<sub>4</sub>@Pd<sub>4</sub>D<sub><i>m</i></sub>A<sub>8–</sub><i><sub>m</sub></i>], and the photoactive yellow protein\n(PYP). Among the results, this study shows that an “all-atom”\napproach is unavoidable for reproducing absorption and CD spectra\nof PYP because one of the main transitions involves a local excitation\non a tryptophan.