Internal rotation barrier of the XH3YH3 (X, Y = C or Si) molecules. An energy decomposition analysis study

In this paper, the barriers of the internal rotation in ethane, methylsilane, and disilane are investigated by the generalized Kohn–Sham based energy decomposition analysis (GKS-EDA) scheme (P. Su, et al. J. Phys. Chem A 118 (2014) 2531). The rotation barriers and the inter-conversion energies from the three geometrical variation processes are decomposed into the electrostatic, exchange–repulsion, polarization, correlation and geometrical relaxation terms. It is concluded that the rotation barriers of the three molecules are all dominated by exchange–repulsion (Pauli repulsion). The geometry relaxation does not make a difference to the origin of the barrier.