Left panel: number of water molecules with a certain number of neighbours in a 60×60 grid as a function of temperature. The temperature is initially set at 10 K and is increased at a rate of 2 K/min to mimic laboratory conditions. The total number of water molecules is 18 000. Right panel: number of pores as a function of temperature. The numbers n in “pore n” indicate the radius of empty spheres in number of grid cells. These numbers are directly related to the size of the pores (pore 6 has a radius of 6×2.75 Å).