• excess free energy;
  • line tension;
  • contact angle;
  • Tolman length;
  • heterogeneity

Due to its complexity, line tension is usually neglected or indirectly estimated in studying heterogeneous nucleation. In this work, we try to provide a direct and quantitative description of it. Within a three-dimensional density functional framework, the total excess free energy and individual energies at different two-phase interfaces are calculated during the droplet or bubble nucleation in binary fluids, and the line tension and contact angle are determined simultaneously. Meanwhile, the contact angle can also be measured directly from the spatial configuration of droplet or bubble. Comparing the calculated and measured contact angles, one can see that a good agreement is achieved for bubble and droplet at solvophilic and solvophobic walls. It is shown that line tension provides a considerable modification of contact angle prediction that is of great importance in engineering applications. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4390–4398, 2013