Assisting calculation of vibrational circular dichroism spectra by molecular tailoring approach

Theoretical investigation of the vibrational circular dichroism (VCD) spectrum requires computationally demanding construction of Hessian matrix elements along with atomic polar- and atomic axial-tensors. The fragmentation-based method, molecular tailoring approach (MTA) [Sahu et al., Acc. Chem. Res. 47, 2739 (2014)], is used for the first time to calculate the VCD spectra of large molecular systems. The accurate computation of these quantities is achieved by reduction of errors arising due to the approximate nature of MTA through the grafting correction from a smaller basis set. The performance of the methodology in reproducing the VCD spectral features is tested out on a variety of molecules, viz. sugars, polypeptides, and proteins using different density functionals with large basis sets. Regardless of the spectral regions, the vibrational peak positions and VCD intensities derived from the current methodology agree well with the full calculation results for these systems. Furthermore, a comparison of gas- and solvent-phase VCD spectra of Oxo-helicene shows excellent agreement with the experimental spectrum in the CDCl3 solvent. This study opens the possibility of an accurate yet inexpensive calculation of VCD spectra of large molecular systems within the MTA-framework.