It could be that the energy required to break the hydrogen bond from random collisions is higher than the theoretical minimum because the angle of a typical col

It could be that the energy required to break the hydrogen bond from random collisions is higher than the theoretical minimum because the angle of a typical collision "wastes" energy in imparting vibration or rotation of the water molecule rather than just imparting "escape velocity". Just a wild guess though. Haven't yet read the article.