Analysis of the VROA signals of helical heptasilanes using an atomistic approach

The VROA signatures of different helical conformers of heptasilane have been analyzed using an atomistic approach. Based on ab initio VROA quantities, the decomposition scheme and its representation under the form of group coupling matrices enable us to highlight the dominant role of the Si atoms for the modes studied. The sum of the contributions from H atoms, on the other hand, is generally negligible, often due to compensations, whereas the heteronuclear Si-H contributions can be important. The dominating VROA signatures are mostly associated with collective wagging, rocking, and twisting motions.