Dissipative effects in the dynamics of N2on tungsten surfaces

The role of electron–hole pair excitations in the dynamics of N2 on W(100) and W(110) is evaluated using a theoretical model that accounts for the six-dimensionality of the problem in the whole calculation. The six-dimensional potential energy surface is determined in each case from an extensive grid of energies calculated with density functional theory. Dissipative effects due to electron–hole pair excitations are introduced in the classical dynamics equations through a friction force. Corresponding electron friction coefficients are calculated for each atom in the molecule with density functional theory in a local density approximation. Our results show that electronic friction plays a very minor role in the dissociative dynamics of N2 in both tungsten faces. A similar conclusion is reached when we calculate the energy lost by the reflecting molecules.