This keyword requests a classical trajectory calculation [Bunker71, Raff85, Hase91, Thompson98] using the Atom Centered Density Matrix Propagation molecular dynamics model [Iyengar01, Schlegel01, Schlegel02]. This method provides equivalent functionality to Born-Oppenheimer molecular dynamics (see the BOMD keyword) at considerably reduced computational cost [Schlegel02].

ADMP belongs to the extended Lagrangian approach to molecular dynamics using Gaussian basis functions and propagating the density matrix. The best known method of this type is Car-Parrinello (CP) molecular dynamics [Car85], in which the Kohn-Sham molecular orbitals, ψ_i, are chosen as the dynamical variables to represent the electronic degrees of freedom in the system. CP calculations are usually carried out in a plane wave basis (although Gaussian orbitals are sometimes added as an adjunct [Martyna91, Lippert97, Lippert99]). Unlike plane wave CP, it is not necessary to use pseudopotentials on hydrogen or to use deuterium rather than hydrogen in the dynamics. Fictitious masses for the electronic degrees of freedom are set automatically [Schlegel02] and can be small enough that thermostats are not required for good energy conservation.

ADMP can be performed with semi-empirical, HF, and pure and hybrid DFT models (see the Availability tab for more details). It can be applied to molecules, clusters and periodic systems. PBC calculations use only the Γ point (i.e., no K-integration).