<italic>Ab initio</italic>path-integral molecular dynamics and the quantum nature of hydrogen bonds

Ab initiopath-integral molecular dynamics and the quantum nature of hydrogen bonds

Feng Yexin¹, Chen Ji¹, Li Xin-Zheng^{2, 3, †,}, Wang Enge^{1, 3}

Quantification of the competition between the quantum fluctuations on the stretching and bending modes. The differences in average shortest heavy-atom distances between PIMD and MD simulations (Δ(X–X), vertical axis) are plotted as a function of the ratio of the projection of the donorX–H covalent bond along the intermolecular axis from PIMD and MD simulations (horizontal axis).xlarger (smaller) than 1 indicates a dominant contribution from the stretching (bending) mode when the NQEs are included. Negative values ofΔ(X–X) indicate that NQEs decrease the intermolecular separation. An almost linear correlation between the two variables is observed. The inset illustrates the geometry used for projecting the donor covalentX–H bond onto the intermolecular axis. The curved red arrow represents the intermolecular bending and the straight blue arrow represents the intramolecular stretching.^[7]