Figure 2.

Histogram of the ${\mathrm{C}}_Q–{\mathrm{C}}_B$ bond fluctuations of ethane from molecular dynamic simulations at 300 K using Hartree–Fock theory with the 6–311+G(d,p) basis set (full QM in black), and hybrid QM/MM potential using the projected hybrid orbitals model with the local force field restraints (PHO in red), with the tetrahedral angles restraints only (Tet in yellow) and without restraints (NR in green).