To track the time evolution of intermolecular interactions with high accuracy, we applied the AIMD methods based on the fragment molecular orbital and effective fragment potential (EFP) methods. The EFP method is particularly suited to performing nanosecond-order AIMD simulations for systems containing several thousand atoms; it has been applied to clarify thermodynamic properties under varying conditions of pressure, temperature, and concentration, due to its high accuracy and efficiency. In this research, a set of ab initio EFP-MD simulations (2.5 ns for production) was conducted on dilute aqueous TMAO solutions (0.18 mmol L -1 ) to clarify the effect of the TMAO solute on the dynamics of the system. For comparison, a dilute aqueous solution of tert-butyl alcohol (TBA, Figure ) was investigated.