Temperature PDF (blue line, left axis) for a 3 nm carbonaceous dust grain, as compared to the formation efficiency (LH mechanism) as a function of temperature (green lines, right axis). The red vertical line marks the mean temperature of the blue PDF. The grain receives a G₀ = 20 radiation field and is surrounded by a 100 K gas with n_H = 10⁴ cm^-3. The energy values correspond to ices.