Molecular dynamics simulation based on the multi-component molecular orbital method: Application to H _5O _2 ~+, D _5O _2 ~+, and T _5O _2 ~+

摘要

We propose a molecular dynamics (MD) method based on the multi-component molecular orbital (MC-MO) method, which takes into account the quantum effect of proton directly, for the detailed analyses of proton transfer in hydrogen bonding system. The MC-MO based MD (MC-MO-MD) method is applied to the basic structures, H _5O _2 ~+ (called "Zundel ion"), and its isotopomers (D _5O _2 ~+ and T _5O _2 ~+). We clearly demonstrate the geometrical difference of hydrogen bonded O ~?O distance induced by H/D/T isotope effect because the O ~?O in H-compound was longer than that in D- or T-compound. We also find the strong relation between stretching vibration of O ~?O and the distribution of hydrogen bonded protonic wavefunction because the protonic wavefunction tends to delocalize when the O ~?O distance becomes short during the dynamics. Our proposed MC-MO-MD simulation is expected as a powerful tool to analyze the proton dynamics in hydrogen bonding systems.