jp0c06313_si_001.pdf (422.88 kB)
Cluster-Weighting in Bulk Phase Vibrational Circular Dichroism
journal contribution
posted on 2020-08-05, 16:45 authored by Jan Blasius, Barbara KirchnerWe
present a cluster-weighting approach for calculating the vibrational
circular dichroism (VCD) spectra of bulk phase systems. Based on the
quantum cluster equilibrium theory, cluster populations are received
via self-consistent field calculations that allow a mixing of differently
sized oligomers at the same time. The thereby obtained cluster weights
are employed for the weighting of individual cluster VCD spectra in
order to calculate an overall gas or bulk phase VCD spectrum. As the
mixing of different oligomer sizes is possible, different structural
motifs and interactions can be included, and explicit solvation, typically
necessary for describing hydrogen bonds, is intrinsically taken care
of, however, without neglecting monomeric structures and different
conformers. We test the sensitivity of Boltzmann and cluster weights
with respect to the level of theory employed and show that cluster
weights are less sensitive. By a constant increase of the oligomer
sizes included in our cluster sets, combined with a continuous truncation
of low populated clusters, we are able to improve the agreement between
theory and experiment until we reach an overlap which allows a certain
assignment of the absolute configuration based on an experimental
bulk phase spectrum. Combined with a computationally cost-efficient
level of theory, this approach provides a valuable tool for the fast
calculation of VCD spectra for bulk phase systems.