Rayleigh-Benard instability in systems presenting a minimum in surface tension

It is shown that in the Benard configuration, when the temperature of the upper surface is exactly Tmin, the Marangoni number is equal to zero and therefore Marangoni convection should be suppressed. The rest state (linearly stable) is unstable with respect to at least one particular type of perturbation, provided that the curvature of surface tension is important and, simultaneously, the initial temperature fluctuation exceeds a critical threshold.