Molecular Dynamics Simulations of Classical Stopping Power

Energy conservation in molecular dynamics simulations of classical systems.

Classical Newtonian dynamics is analytic and the energy of an isolated system is conserved. The energy of such a system, obtained by the discrete "Verlet" algorithm commonly used in molecular dynamics simulations, fluctuates but is conserved in the mean. This is explained by the existence of a "shadow Hamiltonian" H [S. Toxvaerd, Phys. Rev. E 50, 2271 (1994)], i.e., a Hamiltonian close to the o...

Explicit proton transfer in classical molecular dynamics simulations

We present Hydrogen Dynamics (HYDYN), a method that allows explicit proton transfer in classical force field molecular dynamics simulations at thermodynamic equilibrium. HYDYN reproduces the characteristic properties of the excess proton in water, from the special pair dance, to the continuous fluctuation between the limiting Eigen and Zundel complexes, and the water reorientation beyond the fi...

Direct Numerical Tests of Kinetic Theory Collision Integrals with Molecular Dynamics Simulations of Stopping Power in Plasmas

Paul E. Grabowski, Michael S. Murillo, CCS-2; Michael P. Surh, David F. Richards, A. Bruce Langdon, Frank R. Graziani, Lawrence Livermore National Laboratory Molecular dynamics (MD) is used as a validation tool for different stopping models based on kinetic theory. MD is also used to improve those models so they are accurate over a wider range of conditions. Unlike many transport quantities, st...

Molecular dynamics approach to vibrational energy relaxation: Quantum-classical versus purely classical nonequilibrium simulations

Quantum - Classical Molecular Dynamics

We study time integration methods for equations of mixed quantum-classical molecular dynamics in which Newtonian equations of motion and Schrr odinger equations are nonlinearly coupled. Such systems exhibit diierent time scales in the classical and the quantum evolution, and the solutions are typically highly oscillatory. The numerical methods use the exponential of the quantum Hamiltonian whos...