The problem is that there is not an adequate model of the liquid state. The size of the hole can be determined by analyzing the solid matrix. The experimental data for liquid metals are very limited, and for liquid semiconductors even more so. The data that do exist may be questioned because convection can confuse the measurements. Convection is heat and mass transfer by fluid motion.
Convection causes a mixing in the melt beyond that due to pure diffusion.
On Earth it is very difficult to distinguish between the two processes. This research is the study of the fundamental and applied issues regarding diffusion of mass in the liquid state. One cause of diffusion is a concentration gradient. Material concentrated in one location, such as a sugar cube dissolved in the bottom of a cup of coffee, will spread out until it is uniformly distributed, and then the net flow of mass will cease. Diffusion due to concentration gradients is called Fickian diffusion after Adolf Fick, who developed the mathematical expression that describes this behavior.