The present work investigates the coalescence process of two gold nanoparticles for a host of initial temperatures and starting radii in vacuum with the help of molecular dynamics (MD) simulations. Diverse mechanisms of the first sintering stage, characterized by a growing neck region, were found. The results are compared with a phenomenological macroscopic model based on an energy balance and supplemented by a model for the surface variation of the nanosystem. under consideration. The model is also modified to account for the curvature dependence of the melting temperature of the nanoparticles. Accounting for the findings of the MD simulations for the neck growth rate, the validity of the analytical model with the initial temperature and radius of the particle is shown. The calculations were extended to particles having radii between 9.5 and 25 Angstrom. (C) 2004 Elsevier Ltd. All rights reserved.