Ab initio molecular dynamics (AIMD) is a computational method used in theoretical and computational chemistry to simulate the motion of atoms in a molecule. Unlike classical molecular dynamics, which uses empirical interatomic potentials to describe the interactions between atoms, AIMD uses quantum mechanical calculations to obtain accurate descriptions of the electronic structure and interactions of the system.
AIMD starts with an initial configuration of the atoms and uses density functional theory (DFT) calculations to determine the electronic structure and energy of the system. The energy is then used to calculate the forces acting on the atoms, and these forces are used to integrate the equations of motion for the atoms using classical mechanics. The resulting atomic trajectory provides information about the behavior of the system over time, including the dynamics of chemical reactions, the response of a molecule to an external stimulus, and the properties of materials at the atomic scale.
AIMD is a powerful tool for understanding the behavior of complex chemical systems, but it is also computationally demanding, as each time step requires a full DFT calculation. To overcome this limitation, approximate methods, such as Born-Oppenheimer molecular dynamics (BOMD) and Car-Parrinello molecular dynamics (CPMD), have been developed to reduce the computational cost. However, these methods are still computationally intensive and require access to powerful computational resources.