A computer simulation has been carried out to illuminate atomic processes in the fluorination of a dimerized Si(100) surface. The molecular dynamics utilizes a combination of two-atom interactions to represent the overall system potential energy. Distinctly different outcomes arise from a pair of 130-ps simulations that employ identical initial and boundary conditions. For one of these energy is conserved, the heat released by reaction causes substrate melting, and volatile ${\mathrm{SiF}}_3$ and ${\mathrm{SiF}}_4$ products emerge. The other is nonconservative due to periodic reduction of Si momenta to approximate thermal conduction into a bulk substrate; it just avoids melting, yields a passivated surface with all dangling bonds fluorinated, and fails to produce volatile products.

• Received 2 December 1988

DOI:https://doi.org/10.1103/PhysRevLett.62.2144