A three-dimensional analysis of the dynamics of hydrogen isotopes confined within a metal lattice, like palladium or nickel, is presented. It is assumed that the concentration of the hydrogen isotopes, as an atomic fraction, is close to unity and that coherent oscillations of the metal atom electrons near to the Fermi level take place. Coherent oscillations of the Fermi-level electrons in the metal lattice can produce an oscillating electric field within the cell and hence produce a radio-frequency oscillation of ions like protons or deuterons. The trajectories of the ions can be studied by means of the equations of motion. The results show that under proper initial conditions, the closest distance of approach between two ions or between an ion and the nucleus of an atom of the host metal lattice can be reduced below 0.1 Å. An evaluation of the excess of heat production has been done for the D-D reaction within a Pd lattice by approximating the reaction both to an s-wave and a d-wave process, respectively. Last, the effect of the lattice field, which causes the collisions between ions, on the nuclear reaction channel for the D-D reaction is investigated by evaluating the transition probability for a stimulated decay.