However, natural crystals always contain some imperfections known as defects in the lattice. The simplest kind of defect is a point defect, which occurs at a single lattice site. Note the distortion of the lattice in the region around the Vacancy. Sit back and watch the vacancy drift through the lattice. To make the vacancy more obvious, select Show Hole from the Options Menu item.
Diffusion is the movement of point defects through the lattice.
As the temperature is increased, the natural vibrations of atoms becomes amplified so that an atom adjacent to a vacancy may have enough energy to be able to jump into that vacancy, leaving a new vacancy behind it as it does so. We can think of the atoms moving around in this way, but if all the atoms in the lattice were identical, as in a pure metal, then there would be no way to know that anything had happened. Alternatively, we can think of the vacancy as moving through an otherwise still lattice. Under hydrostatic conditions, vacancies diffuse through a crystal lattice in a random way. Increasing the temperature just means they diffuse more rapidly, but still randomly.