Numerical integration of projective Hamiltonian dynamics

Projective Hamiltonian dynamics [S. Melchionna, J. Chem. Phys. 121, 4534 (2004)] is an approach to reduce mode spreading in complex systems, thus improving the performances of Molecular Dynamics simulations. A numerical integration of the dynamics requires proper treatment of the non-separable form of the Hamiltonian, Due to its symplectic nature, the generalized leapfrog scheme is shown to provide robust and reliable numerical trajectories even in the case of stiff projective forces.