A sphere of 1 A radius is generated at the (0, 0, 0) coordinates using the
dot density specified by the user. For each atom (Ai), this sphere is scaled
multiplying the dot coordinates by the correspondent Van Der Waals radius (Ri) 
and translated to the atom coordinates (Xi, Yi, Zi). The dots overlapped to 
near atoms are discarded. This procedure is performed measuring the distance 
between the surface dots of the "Ai" atom and all atomic coordinates for all "n" 
atoms: if it's less than the "An" Van der Waals radius, the dot is overlapped.
This algorithm takes O(n^2) computation time.