XVIth International Workshop on
Quantum Systems in
Chemistry and Physics
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Simulations of Solid-State Vibrational Circular Dichroism Spectroscopy by Using Fragmentation Quantum Chemical Calculations
Jing Ma and Nan Jiang
School of Chemistry and Chemical Engineering, Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University, Nanjing, Jiangsu, 210093, People’s Republic of China
Simulations of vibrational circular dichroism (VCD) spectroscopy of optical active aggregates of chiral molecules in the amorphous solid encounter great difficulties in the description of complicated intermolecular interactions by using the conventional quantum mechanical (QM) methods. The fragmentation approach is applied to calculate the VCD spectra of the covalently bonded oligomers and non-bonded molecular aggregates of (S)-alternarlactam. Starting from the statistically averaged configurations that are sampled from the molecular dynamic simulations, the target oligomers or packing systems are divided into several fragments with a proper treatment of boundary effects on the separated segments. Each fragment is embedded in the background point charges centered on the distant atoms to simulate the long-range electrostatic interactions. The total VCD signals are assembled from the rotational strength of all the fragments. Test calculations on the bonded oligomers and molecular aggregates using fragmentation method show good agreement with the conventional QM results. The fragment-based VCD calculations on molecular aggregates give a better agreement with experimental spectra than the Boltmann-weighted spectra of various possible monomeric, dimeric, and trimeric configurations. The computational cost of fragmentation calculation scales linearly with the number of the molecular fragments, facilitating the future applications to a wide range of the large-sized chiral systems.


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